Portable telephone system

ABSTRACT

A portable telephone system is disclosed in which a plurality of i-th class exchanges, which accommodate key service units of a plurality of portable telephone sets present in each service area, and at least one (i+1)th class exchange which accommodates the plurality of i-th class exchanges through junction lines, are stratified to form an exchange system so that i=1, 2, 3, . . . , and so that the (i+1)th class exchange covers all service areas. The exchange system has a function whereby information which specifies the home area of each portable telephone set and the portable telephone set in distinction from each other is registered in the i-th class exchange and the (i+1)th class exchange, which administer the home area.

This is a continuation of application Ser. No. 07/547,386, filed Jul. 2,1990, which is a continuation of application Ser. No. 07/396,442, filedAug. 21, 1989, which is a continuation of application Ser. No.07/107,418, filed Nov. 25, 1987, all now abandoned.

BACKGROUND OF THE INVENTION

present invention relates to a system for setting up a channel in aportable telephone system using portable telephone sets, which areconnected to a general public telephone network, a private branchexchange network, etc. and which can be carried to any place and arecapable of originating and receiving a call.

At present a variety of mobile communications are in practical use inmany countries. Of them, telephones primarily for voice transmission area domestic maritime mobile radio telephone, a land mobile radiotelephone, a cordless telephone, and a section party telephone within astation yard. These various mobile communications are respectivelyoperated as independent systems; for instance, a cordless telephonecould not start a call when it is brought in a car. This is evident fromthe fact that the cordless telephone and the land mobile radio telephonediffer from each other in many points; for example, they use differentworking frequencies and different control methods for their controlchannels, and in addition, the input radio wave field strength necessaryfor the receiver of the called land mobile radio telephone would not besatisfied with the transmitting power of the cordless telephone.

Further, the cordless telephone generally comprises a portable telephoneset and a key service unit which are connected thereto by way of a radiocommunication circuit and to an exchange by way of a wire communicationcircuit. In addition to this, the telephone set and the key service unitusually form a specific relationship to each other. The telephone setcannot communicate with a key service unit other than the specified oneeven if they happen to lie at a short distance over which radiocommunication could be established between them. Similarly, the keyservice unit is not permitted to communication with other telephone setsthan the specified one.

This is a matter of course in some sense. It is undesirable if aportable telephone set and a key service unit which have no particularrelationship to each other are connected without any conditions, becausethis will incur the possibility of mischarging or intentional shiftingof a charge due on the connected telephone set to an unconnected one.

People have long been waiting eagerly for the appearance of a portabletelephone system which technically overcomes the above-noteddifficulties and enables a person carrying the portable telephone set tomake a call from any place to any place at any time and to receive acall wherever he may go.

Even in a society like our country where the number of telephoneterminals for public communication use is now as large as more thanforty millions and where public telephone sets are accessible everywhereon the streets, not to speak of land mobile radio telephones on cars,train public telephones on Shinkansen trains, and domestic maritimeradio telephones on ships, there still exists a strong demand for such aportable telephone system for the reason given below.

This is because everyone wishes to have a portable telephone for hisexclusive use. That is to say, it would be extremely convenient if aperson carrying the portable telephone could freely use it just like atelephone installed at his home, for there are cases where he feelsaskward, for some reason, to ask for permission to use a telephone atother people's office or home, where no public telephone can be found onthe streets, where anyone does not happen to have small money or atelephone card with him, where no public telephones installed in frontof stores or the like can be used late at night, and where it istroublesome to look for a public telephone at a crowded place like aballpark or area for special events.

The same applies to receiving a call. It would be far more convenientthan in the above cases if anyone carrying the portable telephone couldreceive a call from any place at any time wherever he may go. This isbecause although anyone can make a call from a nearby public telephoneat any time it is unpredictable when he will be called while he is awayfrom his home or office. Moreover, it is impossible, with theconventional telephone system, that two persons communicate with eachother if they are moving in different places.

In addition, the portable telephone will enable an emergency or urgentcall to be made more simply and more quickly than the systems nowemployed. Besides, it would be more convenient if the portable telephoneset could be used for opening a credit (a credit function) or as asubstitute for an identification card.

As described above, there is eager demand for the realization of such anultimate portable telephone even at present.

To meet this demand, various systems have been proposed which are,however, unsatisfactory in many respects.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a system forestablishing a channel in a novel concrete portable telephone systemwhich can be realized in a relatively near future, without thedisadvantages of the afore-mentioned conventional portable telephonesystems, and can essentially be called an ultimate portable telephonesystem.

A portable telephone system in which a plurality of i-th class exchangesaccommodate at least one key service unit of a plurality of portabletelephone sets present in each service area, and at least one (i+1)thclass exchange, which accommodates the plurality of i-th class exchangesthrough junction lines, are stratified to form an exchange system sothat i=1, 2, 3 . . . , and so that the (i+1)th class exchange covers allof the service areas. The exchange system has the function wherebyinformation which specifies a home area predetermined from the serviceareas for each portable telephone set and the portable telephone set indistinction from each other is registered in the i-th class exchange andthe (i+1)th class exchange which administer the home area.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in detail below in comparisonwith prior art with reference to the accompanying drawings, in which:

FIGS. 1 and 2A are block diagrams illustrating examples of conventionalsystems;

FIGS. 2B and 2C are block diagrams illustrating examples of routings inconventional systems;

FIG. 3A is a block diagram illustrating an embodiment of the portabletelephone system of the present invention applied in a subscriber'sstation;

FIGS. 3B, 4A, 4B and 4C are block diagrams illustrating element circuitsconstucting the system of the present invention;

FIGS. 5A, 5B and 5C are block diagrams illustrating embodiments of thepresent invention applied to the whole area of the country;

FIGS. 5D and 5E are block diagrams explanatory of systems employed inthe present invention;

FIG. 5F is a block diagram illustrating a connection system between thesystem of the present invention and another network;

FIGS. 5G and 5H are block diagrams illustrating systems employed in thepresent invention;

FIGS. 5I and 5J are diagrams illustrating examples of frequencyallocations in the system of the present invention;

FIG. 5K is a block diagram illustrating an example of the systememployed in the present invention;

FIG. 6 is a diagram illustrating a signal format employed in the systemof the present invention;

FIG. 7A is a flow shart illustrating signal flows at the outgoing calland the incoming call in the system of the present invention;

FIGS. 7B and 7C are flow charts illustrating signal flows at differentstates in the system of the present invention;

FIGS. 8A, 8B, 8C and 8D are block diagrams illustrating examples of thesystems employed in the present invention;

FIG. 9 is a block diagram illustrating an example of other systememployed in the present invention;

FIG. 10 is a flow chart illustrating signal flows at the outgoing callof another state in the system of the present invention;

FIGS. 11A, 11B, 11C, 11D, 11E, 11F and 11G are flow charts emplanatoryof operations in the present invention; and

FIGS. 12A and 12B are block diagrams illustrating examples of mobiletelephone system according to the present invention.

DETAILED DESCRIPTION

To make differences the present invention and prior art, examples ofprior art will first be described.

A first one of them is to offer a "personal telephone service"(Institute of Electronics and Communication Engineers of Japan, Societyfor the Study of Circuits and Information, Material IN82-21). The systemof this plan (which is called the PID plan) is as follows:

FIG. 1 shows a conceptual drawing of a communication network based onthe PID plan.

Each subscriber is given, for instance, a magnetic card with hispersonal identification number (PID) written therein. The PID written inthe PID card can be used in common to terminals of a fixed telephone, aland mobile radio telephone, a train radio telephone, and so forth. Eachterminal number will hereinafter be referred to as SID. The PID isannounced publicly on a telephone directory, for instance.

The fixed telephone, the land mobile radio telephone, and a terminalwhich will be developed in the future are all equipped with a functionof reading out the PID of the PID card and sending the readoutinformation to the communication network.

The communication network has a master file PF for storing subscriberinformation (the SID, charging information, etc. of each subscriber)corresponding to the PID and is equipped with a connection controlfunction of setting up a communication circuit between calling andcalled terminals on the basis of the call receiving SID which eachterminal has read out of the master file PF.

When arriving at a place where the above-mentioned terminal is provided,each subscriber registers the call receiving SID, using his PID card.When a person who wants to communicate with this subscriber dials thePID in the same manner as is the case with the conventional telephone,an exchange on the side of the calling terminal accesses the PID file,reads out therefrom the SID corresponding to the PID of the calledsubscriber, and connects the calling terminal to the called one in thesame way as in the case of conventional switching connection. As isevident from the connecting sequence, the calling subscriber is able tocommunicate with the called subscriber directly and instantaneously evenif the former does not know where the latter is.

Further, whenever the subscriber uses his PID card for making a call,charging information is recorded in detail on his PID file irrespectiveof which terminal he used. Accordingly, this will preclude the necessityof distinguishing between public telephones and the subscriber'sstation.

When the above-described system has been put to practical use, thesubscriber can make a call from a nearby fixed telephone to a desiredplace and receive a call. However, he cannot originate or receive a callwhile walking the streets, for example.

Moreover, since the centralized PID file (PF) is disposed at only oneplace in one country as shown in FIG. 1, the traffic of an access to thePID file will pose a problem. Now let it be assumed that the file of aPID subscriber living in Sapporo where is located north of Tokyo isaccommodated in the PID file provided in Tokyo. This will be anappropriate assumption since the PID file is placed at only one placethroughout in Japan. Consider that the PID subscriber enters his PIDinformation into a telephone terminal of his next-door neighbor. Thenthe information must be transmitted to the centralized file at Tokyo andrewritten. That is, although the PID subscriber moves only several tensof meters, the data must be transmitted from Sapporo to Tokyo and thenfrom Tokyo to Sapporo (a confirmation signal).

Since such a data transmission takes place on a nationwide scale, theabove system is seriously disadvatageous in terms of traffic andtransmission cost.

Recently another system has been proposed for solving these problems("Proposal of Mobile Message Communication System", Society ofElectronics and Communication Engineers of Japan, Society for the Studyof Communication System, Material CS85-139 (Jan. 23, 1986)).

The above literature states that it is difficult to realize the portabletelephone which is an ultimate means for communication, and proposessuch a specific operative example of the mobile message communication asfollows:

FIG. 2A shows the basic structure of a simple ALOHA system, in whichfrequencies of one up channel and one down channel are allotted to eachradio service zone. A message to a mobile station is sent to a basestation via a digital exchange of a fixed communication network and istransmitted as a packet from the base station. The called mobile stationverifies that it has received the message correctly, and then sends ananswer signal to the calling party via the base station, and the callingparty verifies that the message has reached the called mobile station.The mobile station stores the message and indicates its reception to thecalling party. The called party reads out the stored message.

Calls occur at random from mobile stations. Since the mobile stationsuse the same frequency in the same service zone, a contention will occurwith some probability. In the absence of an answer signal from thecalled party, the calling party re-sends the message. Where the messagecannot correctly be received owing to bad conditions for propagation,the base station detects an error and requests the calling party tore-send the message.

As will be seen from the above, this system is a non-real time, storedcommunication which uses a message (a sort of telegram) instead of avoice and hence does not fulfill the requirement of instantaneouscommunication. Further, the above-mentioned literature does not clearlystate the actual system configuration and other details on the groundthat they are problems to be solved in the future. Accordingly, therealization of this system will take much time for solving the technicalproblems.

The following is a cordless telephone system the service zone of whichis made somethat wider through utilization of the prior art (JapanesePat. Appln. No. 74143/82).

This is a cordless telephone system using cordless telephone stations,which are each connected by radio media to a key-station radio unitprovided at the terminal of each subscriber line of a wire communicationswitching network and then connected via the key-station radio unit tothe wire communication switching network. The cordless telephonestations are each provided with means for automatically transmitting inan encoded form a subscriber's number different from that of thesubscriber line. Each exchange is equipped with means for decoding theencoded subscriber's number to detect the exchange to which the cordlesstelephone belongs and for sending to the exchange positional informationand charge totaling information of the cordless telephone. The exchangehas means for transferring an incoming call or totaling charges on thebasis of the above-mentioned information.

However, this system is based on the assumption that its service areacovers a single limited district or city. Accordingly, in the case ofemploying this system over a wider area such as the Kanto district inJapan, the central districts of Japan, or the nationwide area, theamount of transmission for signal transfers will increase, which willlessen the technical and economical effects of the system, as is thecase with the aforementioned "Personal Telephone Service". In addition,this system achieves at least wide coverage but has the shortcoming thata subscriver's number different from that of the subscriber's line mustbe given as the cordless telephone number.

Moreover, study is being given a mobile communication system whichcombines subscriber telephone systems of respective mobile radiocommunication systems so that each subscriber needs only to have onekind of equipment for connection to the communication network from anyplace (Japanese Pat. Appln. No. 151136/83). This is a mobilecommunication system which is intended to permit economization ofsubscriber's equipment and economic removal of a dead zone in a servicearea. This mobile communication system has a land mobile radio telephonebase station, a portable telephone radio base station connected to onewire communication switching network, and a cordless telephone hostdevice connected to one terminal of the switching network, and eachmobile subscriber's device is arranged so that it can be connected toeither of the base stations and the host device by way of a radiocommunication circuit.

With this system, however, when a cordless telephone subscriber uses thecordless telephone, for example, in a car, radio waved from the landmobile radio telephone base station can be received but radio wavesemitted from the cordless telephone cannot be received by the basestation. The reason for this is that the transmitting power of thetransmitter of the land mobile radio telephone is 5 watts at present,whereas the transmitting power of the cordless telephone is 6milli-watts, which is 1/800 the transmitting power of the land mobileradio telephone.

If the transmitting power of the cordless telephone were increased to 5watts or so, the base station could receive the radio waves from thecordless telephone, enabling communication. However, this inevitablyincreases power consumption, which results in a substantial reduction oftime for which the subscriber can carry the cordless telephone with him,and when a battery of large capacity is employed, the cordless telephonewill become bulky and hence inconvenient to carry. Accordingly, such acordless telephone will be defined as a modification of the land mobileradio telephone rather than the portable telephone.

Therefore, the above system is an inconvenient system appreciablydifferent from the portable telephone system which enables communicationbetween any places at any time.

The four proposed systems mentioned above can be considered asapproaches to the portable telephone system; they fulfill-some of therequirements for the ultimate portable telephone system but are stillinconvenient to users and there is yet much to be done for furthertechnical development.

When a subscriber originates a call, a communication circuit isconnected from a station (the calling station) in which the subscriberis accommodated, via some relay exchanges, to a station (the calledstation) in which the called subscriber is accommodated. Generally thereare a plurality of connection paths in a composite network, and theselection of one of them is referred to as routing. In the telephonenetwork, when communication circuits of a first selected route (In theconnection path, communication circuits from a certain station to thenext station are called a route.) are all busy, communication circuitsof a second route are selected. Where the communication circuits of thesecond route are all busy, a third route is selected. In this way,routes are selected one after another. Such a routing method is referredto as multi-stage alternate routing, and a system which sequentiallyswitches trunks through use of this method is called an alternatetrunking system as shown in FIG. 2B.

To satisfy the above conditions, the telephone network now employs afar-to-near-rotation method which is a king of multi-stage alternaterouting. According to this method, routes from the calling station toexchanges on a multi-stage star network from the calling station to thecalled station are selected in order of their distances from the callingstation, beginning with the longest as shown in FIG. 2C.

This method is advantageous in that extra equipment can be dispensedwith by preferentially using transversal trunks of shorter distances,that the transversal trunks can be used with high efficiency, and thatcalls overflowing the transversal trunks can be processed together withcalls in other sections by a group of alternate communication circuits.With this method, however, since the routing must be performed only bythe station (the calling station) in which the calling subscriber isaccommodated, no optimum route can be set fully taking into account thetraffic densities in other exchanges.

Before starting the detailed description of the present invention,Definition of Technical Terms will be described.

Definition of Terms

Portable Telephone Set

This is one of main constituents of the present invention, which theuser always carries with him for originating and receiving calls byradio through a portable telephone key service unit described later.FIG. 4A illustrates an example of the arrangement of the portabletelephone set. Its radio section is equipped with a multichannel accessfunction, an interference detecting function, and various otherfunctions for ensuring high-quality communications with a highefficiency of the utilization of frequency. A communication signal issubjected to an analog or digital modulation in a modulating section andis transmitted, by a modulated wave with a high degree of privacy, tothe associated portable telephone key service unit. A demodulatingsection demodulates the modulated wave into a voice signal by a processreverse from that in the modulating section, and the demodulated voicesignal is transmitted to a receiving section. The transmitting power ofthe portable telephone set is about 6 milli-watts, substantially equalto the transmitting power of the cordless telephone set now employed.However, the transmitting power level of the portable telephone set maybe decided by system design objects, considering the size of servicearea of each portable telephone key service unit, user's call trafficdensity of the portable telephone using a frequency band, etc.Therefore, the level may usually change from 1 milli-watt to 100milli-watts. The portable telephone set is also equipped with a functionof displaying the PID of the calling subscriber during the reception ofa call and storing the PID. The portable telephone set is given, as anidentification number PID of its own, a number different from those ofother portable telephone sets or terminals of other systems. The PIDnumber may sometimes be referred to simply as PID.

In some cases a plurality of portable telephone sets are provided inassociation with one fixed telephone set described later. For example,in a case where each member of a family of five uses portable telephonesets of different PID numbers, five portable telephone sets areprovided. Of course, these portable telephone sets can each be usedindependently of the others while being carried with the individualmembers of the family. The portable telephone set may given a codenumber to have a key function for preventing it from being used withoutleave or by a third person when it is stolen.

Fixed Telephone Set

The fixed telephone set pairs with each portable telephone set and hassubstantially the same functions as those of a fixed telephone set ofthe cordless telephone now employed by NTT (NIPPON Telegraph andTelephone Corporation) of Japan except in the following points. That is,the fixed telephone set transmits and receives communication signalsbetween it and the portable telephone sets, by radio, and besides, it iscapable of accessing a desired one of portable telephone sets and has afunction of registering, changing and cancelling their positions.

FIG. 3B illustrates in block form the arrangement of the fixed telephoneset. In the present invention, since a third party may use thesubscriber line, it is desirable that the subscriber line be amultichannel path which enables simultaneous communication in two ormore communication circuits. This can easily be implemented when anoptical fiber cable has come into use as the subscriber line. The fixedtelephone set may sometimes be housed in the same unit together with theportable telephone key service unit described later. The fixed telephoneset has self-identification information SID different from those ofother fixed telephone sets, as is the case with the PID. Thisself-identification information is referred to simply as SID in somecases. In this specification the fixed telephone set in the home area ofthe portable telephone set PID₁ is sometimes referred to simply as SID₁.The fixed telephone set has the following additional functions besidesthe function of a telephone set which is usually employed at a telephoneterminal connected by a wire line to PBX or a local switch (hereinafterreferred to as a first class exchange).

(1) Function of displaying the current position (the registerd position)of the portable telephone set;

(2) Function of receiving a call on behalf of the portable telephone setwhen the latter cannot receive the call;

(3) Function of transfer a call to the portable telephone.

Portable Telephone Key Service Unit

This is associated with the afore-mentioned portable telephone set, fororiginating and receiving telephone calls by radio. This key serviceunit is sometimes housed in the same unit together with the afore-saidfixed telephone set in the case where the latter is provided.

The portable telephone key service unit can be obtained by equipping acordless telephone key service unit now in use, described later, withsome additional functions. FIG. 4B shows the arrangement of the portabletelephone key service unit. The portable telephone key service unit willhereinafter referred to simply as SID in some cases. The portabletelephone key service unit in the home area will also hereinafter bereferred to simply as SID₁.

The portable telephone key service unit may be installed on a pole in apublic garden or on the side of the street for public usage. In thiscase, there is no fixed telephone set afore-mentioned.

General Telephone Set

This is not the portable telephone set but is a telephone set which anordinary telephone subscriber uses.

PBX

This accommodates ordinary general telephone sets and has a telephoneexchange function in an office or the like and, besides, a function ofaccepting, changing and cancelling the position registration of theportable telephone set. The term PBX is also used for expressing an areahaving a spatial expanse placed under control of the PBX or hardwareitself which implements the telephone exchange function. In thisspecification the term PBX is sometimes used to be included in the firstclass exchange.

First Class Exchange

Usually this accommodates telephone sets in an exchange area, such asresidence telephones in general, and handless calls from and to theexchange area. This exchange has, in addition to the telephone exchangefunction, a function of processing subscriber information (functions ofaccepting, changing and cancelling the position registration of theportable telephone set and a charging function) and a telephonetransmitting and receiving function. Further, the exchange has an AI(Artificial Intelligence) function of discriminating voice dial signals(voice signals "one, two, three, . . . in place of dial signals 1, 2, 3,. . . 9, 0)from the portable telephone set, converting the voice signalsto corresponding numerals, and returning them to the portable telephoneset. This exchange usually means an exchange which is accommodated in alocal telephone exchange, but it is also used to mean an area having aspatial expanse in which are included telephone sets and subscriberlines placed under control of the local telephone exchange and hardwareitself which implements the telephone exchange function. This is what iscalled an end office in the NTT telephone network as shown in FIG. 5A,and this will hereinafter be referred to simply as KTC-I in some cases.

Reference to telephone sets and portable telephone sets which the firstclass exchange administers means the fixed telephone set and theportable telephone key service unit connected via subscriber lines tothe first class exchange, the portable telephone sets provided inassociation with the key service unit, and general telephone stations. Asubordinate fixed telephone set is also used as synonymous with theadministered fixed telephone set. This exchange has an interface with afirst class radio base station for calling portable telephone sets overa wide area.

A higher-ranking exchange means a second class or higher class exchangedescribed later.

Second Class Exchange (KTC-II)

This exchange ranks above a plurality of first class exchanges and hasfunctions of relaying and switching calls between the first classexchanges placed under its control and ordinary outgoing and incomingcalls of other exchanges, and besides, functions of processingsubscriber information (functions of accepting, changing and cancellingposition registration) for portable telephone sets. Further, thisexchange means an exchange housed in a telephone exchange which covers adistrict usually including a plurality of local service areas, and thisterm is also used to indicate an area having a spatial expanse which thetelephone exchange dominates, and hardware itself which implements thetelephone exchange function. In the NTT telephone network this termmeans an exchange which is housed in a toll center provided for eachlocal city, and will hereinafter be referred to simply as KTC-II in somecases.

When reference is made in this specification, to an exchange andtelephone sets administered by (or subordinate to) the second classexchange, it implies all terminals such as the first class exchangeconnected via a trunk line to the second class exchange and portabletelephone sets administered by the first class exchange.

Moreover, an exchange of a rank higher than the second class exchange isa third class exchange connected via a trunk line to the second exchangeor a fourth or fifth class one which is further connected to the thirdclass exchange via a trunk line.

Third Class Exchange (KTC-III)

This exchange ranks above a plurality of second class exchanges and hasfunctions of relaying and switching calls between the second classexchanges placed under its control and ordinary outgoing and incomingtelephone calls other exchanges, and besides, functions of processingsubscriber information (functions of accepting, changing and cancellingposition registration) for portable telephone sets. This exchangecontrols a district including a plurality of service areas each placedunder control of the second class exchange, and is also used to for anarea having a spatial expanse administered by the third class exchangeor hardware itself which implements the telephone exchange function. Inthe NTT telephone network the third class exchange means an exchangewhich is housed in a distric center provided in each of cities (70cities) of the prefectural capital class, and this exchange willsometimes be abbreviated as KTC-III in this specification.

Fourth Class Exchange (KTC-IV)

This exchange ranks above a plurality of third class exchanges, covers adistrict including several district areas, and has functions of relayingand switching calls between the third class exchanges placed under itscontrol and ordinary outgoing and incoming telephone calls of otherexchanges, and besides, functions of processing subscriber information(functions accepting, changing and cancelling position registration) forportable telephone sets. The term "fourth class exchange" is also usedto for an area having a spatial expanse which this exchange controls, orhardware itself which implements the telephone exchange function. Thisexchange has an interface with a fourth class radio base station forcalling portable telephone sets over a wide area or a land mobile radiotelephone exchange of the land mobile radio telephone system nowemployed. In the NTT telephone network the "forth class exchange" meansan exchange which is accommodated in a regional center. The exchangewill sometimes be referred to simply as KTC-IV.

In the NTT network this exchange is installed in eight major cities suchas Tokyo, Nagoya, Osaka, etc. throughout the whole country area.

Fifth Class Exchange (KTC-V)

This exchange ranks above a plurality of fourth class exchanges and hasfunctions of relaying and switching ordinary outgoing and incomingtelephone calls of the fourth class exchanges, functions of processingsubscriber information (functions of accepting, changing and cancellingposition registration) for portable telephone sets and a telephoneoriginating and terminating function. This term is also used for an areahaving a spatial expanse which this exchange administers, or hardwarewhich implements the telephone exchange function. This exchange willsometimes be referred to simply as KTC-V. Further, this exchange has aninterface with a fifth class radio base station (a satellite) forcalling portable telephone sets over a wide area.

In Japan it is desirable that this exchange be placed at one place(Tokyo). Moreover, this exchange has an international telephone exchangefunction.

n-th Radio Base Station for Calling Portable Telephone Sets over a WideArea (n=1, 2, 3, 4, 5)

The portable telephone set is usually used in association with theportable telephone key service unit; this radio base station is one thatenables the portable telephone set to receive a call in places where thecondition of radio waves propagation is poor and where there is noportable telephone key service unit close by, for example. Using strongradio waves emitted from this base station, basements and underggroundshopping centers in cities would also be included in its service area.The field strength of radio waves from the first to fifth class radiobase station and the conditions for their installation are substantiallythe same as in the case of a pocket pager calling radio base station nowin use. This radio base station performs wide-area calling and sends outcommunication signals over a service area which is an area administeredby an n-th class exchange. The second class and higher-ranking radiobase stations sometimes use the same facility as the first class radiobase station.

The fourth class radio station is also employed for an incoming call tothe portable telephone set mounted in a car, train, airplane, orhigh-speed vehicle. The field strength of sending radio waves of thisradio station and the conditions for its installation are almostidentical with those of the pocket pager calling radio station nowemployed.

The fifth class radio station is incorporated in a satellite, forproviding services for portable telephone sets mounted in ships on anocean and airplanes above an ocean, and used in high mountains such asthe Japan Alps.

These radio base stations send out call signals and communicationsignals under control of the n-th class exchange which has an interfacewith the radio base stations.

There are cases where the call signal only produces an incomingindicator tone (ringing) in the portable telephone set and thecommunication is caused to take place via the nearest portable telephonekey service unit and where call signal contains communicationinformation to the called telephone set when no communication can beexpected because of the absence of radio equipment close by.

Radio Channel (Radio Communication Circuit)

This refers to that section of a signal transmission line used in thepresent system which employs radio waves. The radio channel issubdivided into a control channel (a control circuit) and acommunication channel (a communication circuit). When the same channel(communication circuit) is used as both of them, it will be referred tosimply as a radio channel (a radio circuit).

While the present invention is described as being applied to a systemwhich has both of the control channel and the communication channel, theinvention is also equally applicable to a system adapted to use only thecommunication channel throughout the system. In such an instance, thecontrol channel in the disclosure of the present invention should readas the communication channel and a shift to the communication channelshould read as the use of the local communication channel; further, in acase where a plurality of communication channels are used, it isnecessary only to provide a function of seizing an unused one of them bycyclically retrieving them.

Control Channel (Control Circuit)

Signals, which the user exchanges, prior to the start (or after the end)of communication, with the portable telephone key service unit or widearea portable telephone calling i-th class radio base station forcausing it to register the position of his portable telephone set and tooriginate and receive calls therethrough, will hereinafter be referredto as control signals and the transmission line therefor as a controlchannel (a control circuit). Although in the present invention thecontrol channel means mainly the radio system, the term "controlchannel" will also be applied to control signal transmission lines,mainly formed by wire systems, between the portable telephone keyservice unit and an i-th exchange, between the i-th exchange and a j-thexchange (where i=1, 2, 3, . . . n and j=1, 2, 3 . . . n), and betweenwide area portable telephone calling i-th radio base stations whichtransmit and receive control signals in association with the i-thexchange.

In some cases, the control channel and the communication channel sharethe same transmission line or use it on a time-shared basis. The controlchannel over which the control signal is flowing for transmission towardthe telephone network (correctly speaking, the n-th class exchange) asviewed from the portable telephone set will be called an upward channeland the control channel of the reverse direction therefrom as a downwardchannel. There are cases where the control signals from the portabletelephone key service unit and the portable telephone set aretransmitted at all times and where they are transmitted as required.

Communication Channel (Communication Circuit)

This term will be applied to a transmission line over which user'sactual communication signals (also including image data signals in thecase of a new media) are transmitted for outgoing and incoming calls ofthe portable telephone set. In the present invention the communicationchannel which uses a radio transmission line is mainly between theportable telephone set and the portable telephone key service unit, butsometimes the control channel from the wide area portable telephone setcalling i-th radio base station is also used as the communicationchannel. Furthermore, the communication channel is also employed forcommunication between the portable telephone key service unit and thefirst class exchange and between the i-th and j-th exchanges (where i=1,2, 3, . . . n and j=1, 2, 3, . . . n) which use wire systems as maintransmission lines, and for communication with a computer or the likewhich is used in a portable telephone system of a verification mode. Thecommunication channel over which communication signals are flowing fortransmission toward the telephone network (correctly speaking, the n-thclass exchange) as viewed from the portable telephone set will bereferred to as an upward communication channel (an upward communicationcircuit) and the communication channel of the reverse directiontherefrom as a downward communication channel (a downward communicationcircuit).

Subscriber Information Memory Section

This is a function which the first to fifth class exchanges eachpossess. The exchange stores various information about each portabletelephone set user (outgoing and incoming call information, positionregistration information, charging information, and special informationsuch as credit information) in this section, reads out therefrom,changes, and cancels these pieces of information, and further theexchange exchanges these pieces of information between its subscriberinformation memory section and that of a higher-or-lower-rankingexchange. The subscriber information memory section is divided into (1)a position registration information storing section, (2) a charginginformation storing section, and (3) an individual subscriber's specialinformation storing section. The subscriber information memory sectionwill sometimes be referred to simply as MEM or a memory section.

The portable telephone key service unit also has a functionsubstantially identical with the subscriber information memory section.The portable telephone set also possesses a function of storing,changing and cancelling information such as radio channel numbers andthe SID of the key service unit with which it communicates.

Home Area

This means an area with a radius of about 25 meters (This is suitable ontransmission power of 6 milli-watts. If transmitter power of radio waveis changed, this figure will be reduced or expanded accordingly.) inwhich the portable telephone set is always placed and is able tocommunicate with the portable telephone key service unit to which itbears a parent-chiled relationship. The hatched circle in FIG. 8A showsthe home area of the portable telephone set PID₁. Incidentally it isnormal to install in the home area the fixed telephone set which pairswith the portable telephone set (though not always necessary). Telephonerates in a roam area are all charged to the account of the portabletelephone set or fixed telephone set placed in the home area.

Roam Area

This is an area in the case where the portable telephone set is usedoutside the home area.

The roam area is subdivided into the following five areas according tothe distance from the home area.

Roam Area in the Same PBX

This is an area except the home area in the same PBX containing the homearea of the portable telephone set. Usually the portable telephone setfor use in an exterprise utilizes this area. The area indicated by thebroken line in FIG. 8A is the roam area in the same PBX.

First Class Roam Area

This is an area in which the portable telephone set is used except itshome area in the same area as a local exchange area in which generaltelephones are accommodated (an area which is occupied by terminalsaccommodated in the first class exchange, to be precise). The areaindicated by the broken line in FIG. 8A is the first class roam area.Portable telephone sets for general residence use are often used in thisarea.

The area will sometimes be referred to simply as the KTC-I roam area.

Second Class Roam Area

This is an area in which the portable telephone set is used except thefirst class roam area in an area administered by a toll center (thesecond class exchange, to be precise).

This area will sometimes be referred to simply as the KTC-II roam area.

The area surrounded by the broken line in FIG. 8B shows the second classroam area.

Third Class Roam Area

This is an area in which the portable telephone is used except thesecond class roam area is an area administered by the third classexchange.

This area will sometimes be referred to simply as the ITC-II roam area.

The area surrounded by the broken line in FIG. 8C shows the third classroam area.

Fourth Class Roam Area

This is an area in which the portable telephone set is used except thethird roam area in an area administered by the fourth class exchange.

This area will sometimes be referred to simply as the KTC-IV roam area.

The area surrounded by the broken line in FIG. 8D shows the fourth classroam area. When the position of the portable telephone set mounted on acar, airplane, or ship is registered, it is regarded that the portabletelephone set lies in the fourth roam area.

Fifth Class Roam Area

This is an area in which the portable telephone set is used except thefourth class roam area in an area administered by the fifth classexchange. In the case of Japan, the whole country is covered by thisarea except the fourth class roam area. It is assumed that the area inwhich the portable telephone set owner of Japan uses in a foreigncountry is this area.

Portable Telephone System of Cordless Telephone Mode

This is a system in which a key service unit (also called a connectingdevice) of the cordless telephone system now employed is used as radioequipment for communication with the portable telephone set. Of course,it is a precondition, in this case, that the key service unit of thecordless telephone has a modified or additional function so that theportable telephone set may exhibit the desired communicating function.

The telephone system of this mode is broken down into the followingthree systems.

Portable Telephone System of Residential District Mode

This is a system in which the portable telephone key service unit isinstalled in an indevidual house or on the external wall thereof mainlyin a residential area of a city or village and a radio section isestabished between the key service unit and the neighboring portabletelephone set. This system is usually suitable for use in a case wherethe communication traffic is not to heavy and the distribution densityof the key service units is uniform throughout the residential area. Theportable telephone key service unit sends out the control signal only asrequired, and only its receiver is always in operation (in the waitingstate) in a predetermined control channel. Despite the residential area,however, there are cases where the traffic of a specific portabletelephone key service unit is large and where the traffic increasestemporarily and suddenly when an accident or disaster occurs. To copewith such a situation, this system is configured so that it can beswitched provisionally to a portable telephone system of anoffice-blocks mode described later.

Portable Telephone System of Continuous Position Registration RequestMode

This is a system which is used when the portable telephone set deliversposition registration request signals continuously or at regularintervals based on a certain rule. This system is used in the caseswhere the portable telephone set user moves in the services area of theportable telephone system of the residential district mode, where henotifies the KTC-I of his current position, and where he wishes toensure receiving an incoming call.

Portable Telephone System of Business District Mode

In a place or area where there is always a crowd of people and thecommunication traffic is heavy and varies greatly, such as a street ofbusiness buildings, busy street, area for special events, large marketplace, or large place of business in an urban area, portable telephonekey service units are installed both inside and outside each building,on public facilities such as telegraph and electric light poles and onthe walls of public buildings. This system is used for establishing aradio communication circuit between each of such key service units andthe neighboring portable telephone set.

The portable telephone key service unit always sends out the controlsignal, and the portable telephone set is capable of registering itsposition and originating and receiving calls by seizing the controlsignal. The portable telephone key service unit normally has onecommunication channel, but in some cases a plurality of communicationchannels are made simultaneously available in the same place inaccordance with the communication traffic.

According to the type of the business district, there is an area inwhich the traffic markedly decreases late at night and on holidays; inthis case, this system is configured so that it can be switched to theportable telephone system of the residential district mode describedabove.

Portable Telephone System of Pocket Pager Mode

This is a system which employs a call wave of the existing pocket pageras a downward control channel to the portable telephone set, fornotifying it of an incoming call thereto. Under certain circumstancesinformation to the called portable telephone set is contained in thecall wave.

Portable Telephone System of Land Mobile Radio Telephone Mode

This is a system which is used when the portable telephone, brought in acar subscribed to the existing land mobile radio telephone system,performs communication through connection with various equipment of thecar telephone. It is a matter of course, in this instance that the landmobile radio telephone system has a modified or additional function forpermitting the use of the portable telephone set.

Portable Telephone System of Train Radio Telephone Mode

Portable Telephone System of Maritime Mobile Telephone Mode

Portable Telephone System of Maritime Satellite Communication Mode

Portable Telephone System of Aircraft Radio Telephone Mode

Each of these four systems is one that enables the portable telephoneset of the present invention to perform communication, using a part ofradio telephone equipment installed on the respective vehicle. It is amatter of course that the existing equipment has its function modifiedor is added with a new function.

Portable Telephone System of Wide Area Calling Mode

This means that the portable telephone set is in a state in which it isable to receive radio waves from a wide area portable telephone setcalling n-th class radio base station (where n=1, 2, 3, 4, or 5).

Portable Telephone System of Identification (Ownership Identification)Mode 5 The portable telephone set is used not as a communicationterminal but as a credit card, identification card, or cash card forwithdrawing money from a bank account. It is a matter of course, also inthis case, that the communicating function of the portable telephone setis effectively utilization.

In view of the above technical terms, the present invention will bedescribed below.

CONSTITUTION AND OPERATION OF THE INVENTION

(1) Functions and Features of Main Components (Devices) of the PresentInvention

FIG. 3A illustrates the arrangement of the portable telephone system ofthe present invention as being applied in a usual house or officebuilding. A first class exchange (KTC-I) shown at the lower left-handside in FIG. 3A and a portable telephone key service unit in the houseat the lower right-hand side are interconnected through a subscriberline. In the house there is provided the portable telephone key serviceunit which is one of the main components of the present invention, andthis is connected to a portable telephone set by radio and a fixedtelephone set by wire. Shown in the upper part of FIG. 3A are the maininternal constitutions of the portable telephone key service unit andthe portable telephone set. A desired frequency can be employed as theworking frequency, so long as it is suitable for use in mobilecommunication and permitted by the government authorities; however, itis assumed that this example employs a 250/400 MHz band as in the caseof the NTT cordless telephone.

FIG. 3B is a block diagram showing the constitution of the fixedtelephone set, which is connected to the portable telephone key serviceunit via a hybrid circuit H. The constitution of the fixed telephone setwill hereinbelow be described. In FIG. 3B a dial and signal transmittingsection 31 is actuated for originating a call. The dial and signaltransmitting section 31 is added with a transmitter 36, a talkie forservice during the absence of the called subscriber, and an SID and PIDmemory which permits the transmission of a dial signal with one touch ofa finger when originating a call. The signal sent out from the dial andsignal transmitting section 31 is stored in an outgoing call informationmemory 33 and at the same time it is displayed on a display 40 undercontrol of a controller 34. This signal is used for transferring anincoming call to the subscriber's registered position throughutilization of the information (SID, PID) when the subscriber is absent.On the other hand, an incoming call to the fixed telephone set occurs inthe case where the power source switch of the portable telephone setcombined with the fixed telephone set is OFF, that is, where theportable telephone set is not in the stand-by state, or in the casewhere an incoming call to the portable telephone is transferred to thefixed telephone set at certain timing when the portable telephone setcannot receive the incoming call because its power source switch happensto be in OFF state or for some other reason although it is not in itshome area but stays in any one of the roam areas. In this instance asignal receiver 32 actuates to ring a bell 38, and when off-hooking, theuser can hear the calling subscriber's voice through a receiver, thusstarting talking. Further, information about the incoming call thusreceived is stored in an incoming call information memory 35.

This system is configured so that the portable telephone key serviceunit is able to communicate with a desired portable telephone set aslong as the latter stays in an area in which communication can beestablished therebetween. Accordingly, there will occur with a certainprobability, though low in terms of traffic, a situation in which whenthe subscriber is about to use the portable telephone set PID₁ or fixedtelephone set (SID₁) at his home, the portable telephone key serviceunit is already in communication with another (a third party's) portabletelephone set. This does not matter when two or more communicationchannels are available; but when only one channel might be available atan early stage of the introduction of this system, it is indicated onthe display 40 of the fixed telephone set that no outgoing call can bemade. This is achieved in the following manner. Where the portabletelephone key service unit is being used, a busy signal is sent from asubscriber line interface circuit in the key service unit shown in FIG.3A and the busy signal is received by the signal receiver 32 of thefixed telephone set and is displayed on the display 40 under control ofthe controller 34.

Moreover, in this instance the owner of the fixed telephone set candemand the third party to early terminate the communication with theportable key service unit, by sending out a clear request signal throughuse of the dial and signal transmitting section 31 of the fixedtelephone set. The clear request signal is transmitted to the portabletelephone key service unit, from which it is applied, as an audible toneor a control signal of the upper or lower side-band frequency, via atransmitter of the key service unit (shown in FIG. 4A) to the portabletelephone set engaged in communication with the third party.

The internal structure of the portable telephone set is depicted in FIG.4A, which will be described in detail later. The above-said clearrequest signal is received by its receiver, as a signal of an audiblefrequency, or the reception of the clear request signal is indicated ona display which indicates whether it is possible to make an outgoingcall and receive an incoming call.

In such a situation, if the portable telephone user moves about 20 to 25meters, he can continue the communication with the third party bysetting a new channel between his portable telephone set and a portabletelephone key service unit installed there. In a case where the usercontinues the communication staying at the same place in disregard ofthe reception of the clear request signal, it is possible to put an endto the communication by transmitting a disconnect signal (a clear-downsignal) to the portable telephone set after a certain elapsed time byuse of a timer 1-7 built in the portable telephone key service unit.

Next, the portable telephone key service unit will be described. Theone-dot chain line block at the left-hand side shows the internalstructure of the key service unit. The key service unit is connected viaa subscriber line interface circuit 1-8 to a subscriber line and a fixedtelephone set. The telephone signal is connected via a controller 1-3 toa transmitter 1-5 and a receiver 1-2. The control signal is used forissuing an instruction via the controller 1-3 to a "synthesizeroscillator" 1-4 to acquire a desired communication channel.

The timer 1-7 in FIG. 4B is used for obtaining charging information inthe case of an outgoing call from the portable telephone set and forgenerating the timing for sending the clear request signal to the busyportable telephone set in association with a control signal generator1-6. Furthermore, in a case where when the portable telephone user hasmoved from one place to another during communication the relativedistance between the portable telephone set and the key service unitincreases and the radio wave field strength value of the input to theportable telephone set becomes so small that the speech quality isdeteriorated (which is detected by a radio wave field strength detector1-9), the control signal generator 1-6 applies a channel change-overrequest (or disconnect) signal to the portable telephone set, causing itto search for a nearly portable telephone key service unit.

Next, a description will be given of a function of changing the mode ofthe control signal which is sent out from the portable telephone keyservice unit. A control mode switching circuit 1-10 in FIG. 4B shows amode switching circuit for siwtching between an as-required-transmitmode and a normally-transmit mode in response to an instruction from atraffic monitor of the first class exchange as shown in FIG. 5A.Assuming, for example, that when a switch SW of the control modeswitching circuit 1-10 is held on the one contact S₁ the portabletelephone key service unit is in the as-required-transmit mode, it canbe switched to the normally-transmit mode by changing over the switch SWto the other contact S₂. As already described in the Definition ofTerms, the portable telephone key service unit is usually held in theas-required-transmit mode when it is installed in a residential area (ina residence), whereas the key service unit, when installed in a businessdistrict, is usually in the normally-transmit mode. Sometimes theportable telephone key service unit includes a traffic measuring section(1-11 in FIG. 4B which performs the same function as that of the controlmode switching section 1-10.

Referring next to FIG. 4A, the internal structure of the portabletelephone set.

In FIG. 4A the portable telephone set has its receiving and transmittingmixer outputs connected to the portable telephone key service unit, andhence is ready for radio communication. A signal received from theportable telephone key service unit is applied via the receiving mixerto an amplifier, the amplified output of which is provided to ademodulator. A part of the demodulator output is applied to a ringer(R). The ringer (R) is adapted to ring upon receiving from the wide areaportable telephone calling n-th class radio base station (where n=1, 2,3, 4, or 5) such a signal as described later. The remaining part of thedemodulator output is applied to the receiver and the controller. Thesignal applied to the receiver is used for actuating it. Next, theoperation of the controller will be described. Upon turning ON of thepower source of the portable telephone set, the controller usuallydecides that the portable telephone set stays in the service area of theportable telephone system of the residential district mode, andregisters the position of the portable telephone set in the followingmanner. The controller controls a transmitting frequency synthesizer sothat a position register request signal can be sent out through apredetermined control channel (#1 in Table 1). At the same time thecontroller controls a reveiving frequency synthesizer to acquire apredetermined down control channel from the portable telephone keyservice unit. If the down control channel cannot be acquired, thecontroller decides that the portable telephone set stays in the servicearea of the portable telephone system of the business district mode, andstarts sweep for acquiring the down control channel. In many cases thecontroller succeeds in acquiring the down control channel at this stageand registers the position of the portable telephone set. If thecontroller should fail, it would decide that the portable telephone setstays in a dead zone, and would proceed to the acquisition of a controlsignal from the aforementioned wide area portable telephone set callingn-th class radio base station. In this case, however, the controllerholds the receiving frequency synthesizer in the state of receiving thedown control channel of the wide area calling i-th class radio basestation and the down control channel of the portable telephone keyservice unit alternately with each other, regardless of whether or notthe control signal from the n-th class radio base station could beaquired. When receiving a call signal contained in a wide area callingdown control signal, the controller actuates the bell to ring and triesto catch a control signal from the portable telephone key service unit.If the control signal could be acquired, a blue lamp (OK) is lighted onthe display, and if not a red lamp (NO) is lighted. Further, thecontroller controls the transmitting frequency synthesizer to make itpossible to generate a predetermined communication (or control)frequency, and controls a roam area communication information memory anda self-identification (PID) memory.

Where the portable telephone set is used in the business district alone,software can be set so that the turning ON of the power source isimmediately followed by the operation of the business district modeinstead of the residential district mode, or that only when the downcontrol signal could not be acquired by the operation of the businessdistrict mode, the operation of the residential district mode is carriedout. Moreover, it may also meet the user's purpose, in some cases, tokeep the portable telephone set waiting in the wide area calling mode,without registering its position in the cordless telephone mode. Thesemodifications can easily be achieved.

Besides, the controller has the following function. In the case wherethe portable telephone subscriber is about to make an outgoing call fromhis portable telephone set in the home area, if the portable telephonekey service unit happens to be engaged in communication with anotherportable telephone set in a certain roam area, the red lamp (NO) displayis provided on the display, indicating that no outgoing call can bemade. That is, since the portable telephone key service unit does notrespond to a communication channel assign request from the subscriber'sportable telephone set through the upward control channel (because thekey service unit is busy), the controller decides, after a certain lapsetime, that no outgoing call is possible, and makes the display provide adiplay to that effect.

However, when the portable telephone key service unit is capable ofsimultaneous communication in two or more channels, the aboveexplanation need not be taken into account because one of the channelsis used exclusively for communication with the portable telephone set inthe home area.

A continuous position register request signal generator and a timer inFIG. 4A are employed also for sending out position register requestsignals from the portable telephone set at regular intervals.

In the portable telephone system of the residential district mode thedown control signal from the portable telephone key service unit is sentout only when necessary, not at all times. Accordingly, even if theportable telephone set has moved out of the service zone of a certainportable telephone key service unit and into the service zone of theneighboring portable telephone key service unit, the registered positionof the portable telephone set would not be changed unless the portabletelephone set originates a call or sends out a position register requestsignal; therefore, no incoming call is made in the cordless telephonemode. In order to avoid this, the controller is equipped with theabove-mentioned function by which position register request signals canbe sent out from the portable telephone set in succession or at regularintervals (or at random).

The portable telephone set is further provided with a switch (SW3 inFIG. 4A) for switching between a continuous position register requestmode and the as-required transmit mode.

Incidentally, even if the portable telephone set has been set in thecontinuous position register request mode, when it enters the servicearea of the portable telephone system of the business district mode, itwill automatically stop the continuous transmission of the positionregister request signal after having catched the down control signalfrom the portable telephone key service unit, and the portable telephoneset will be switched to the as-required transmit mode for the up controlsignal. It is also possible, however, to keep the portable telephone setin the normally-transmit mode for (VID-PID).

The continuous position register request mode is suitable for use in thecase where it is desirable to always locate, for example, at an office,the current position of a doctor, insurance canvasser or like person, orwhere it is desirable to ensure the reception of an incoming call tothem while they are from their offices or the like.

The portable telephone set is, in principle, capable of displaying andstoring the PID of the calling party in communication therewith.Sometimes the portable telephone subscriber wants to know subscriberinformation such as the SID of the portable telephone key service unitcommunicating with the portable telephone set. In this instance, it isnecessary only to depress a function button (#, for example) of the dialsection, by which the controller reads out, from the roam areacommunication information memory, information about the nearest portabletelephone key service unit, i.e. the SID of the key service unit incommunication with the portable telephone set. Where the portabletelephone is in its stand-by state after having its position registeredin the portable telephone key service unit, the SID of the latter can bedisplayed, without the necessity of exchanging radio waves between them,simply by depressing the function button of the dial section. Thisfunction is convenient for it can be used not only for the above purposebut also for guidance, for example, by displaying the address of a placewhere the portable telephone subscriber has lost his way.

Besides, the portable telephone set has a function of displaying thetelephone number of the calling party if its address is known partly orwholly. That is, when the address of the calling party is transmitted,with voice, to the first class exchange, it is identified by its voicesignal identifier, and for verification, a prefectural ID, a city ID, atown ID, etc. described later, are sent back to the calling portabletelephone set, and they are displayed on its display.

When the dial signal, voice signal, or control signal is transmittedfrom the portable telephone set, it is applied first to a modulator, theoutput of which is provided to a transmitting amplifier, the output ofwhich is, in turn, applied to a mixer for converting its frequency to afrequency specified by the controller. The frequency-converted signal isthus transmitted from a transmitting antenna.

The above has described in detail the external functions and theconstitutions of the portable telephone key service unit, the fixedtelephone set and the portable telephone set. Now, a description will begiven of basic functions of the system of the present invention whichutilizes them.

i) At a place where the portable telephone set is usually used (thesubscriber's home or desk in his office, which will hereinafter bereferred to as the home area), it operates in the cordless telephonemode which is now employed by the NTT.

ii) In many cases the fixed telephone set is provided which isassociated with the portable telephone set mentioned above in i) and hasthe SID number. The fixed telephone set is connected to the CO line inthe same manner as in the case of an ordinary telephone set, but unlikethe ordinary telephone set, it has an incoming call transfer function, afunction of displaying the current position of the portable telephoneset, and various other functions.

iii) The portable telephone set is given the PID (theself-identification number) different from those of other portabletelephone sets or other system terminals. When originating a call ordemanded by the portable telephone key service unit, the portabletelephone set automatically sends out its PID signal. (The PID of thisportable telephone set will hereinafter be referred to as PID₁.)

iv) When having originated a call outside its home area, the portabletelephone set stores, in its "roam area communication informationmemory", the roam area SID (the terminal identification number) which issent from the portable telephone key service unit which communicateswith the portable telephone set.

v) Upon turning ON its power source, the portable telephone setautomatically transmits its PID signal through the transmitting controlchannel of the cordless telephone mode of the home area. This willhereinafter be referred to as the "position registration" in the homearea or roam area. The flow of operation in this instance will bedescribed later.

vi) The portable telephone set has a function by which when the portabletelephone set has received an incoming call made in the wide areacalling mode but cannot answer it owing to the absence of the portabletelephone key service unit in the vicinity of the portable telephoneset, it stores the calling subscriber's number in its PID roam areaoutgoing call communication information memory for a certain period oftime and then answers the calling subscriber when having become capableof doing so as a result of movement of the portable telephonesubscriber.

Next, a description will be given of the subscriber information memorywhich is provided in each of the first to fifth class exchanges andwhich is one of the features of the present invention. FIG. 5Billustrates the stratification of the first to fifth class exchanges.The first class exchange administers the portable telephone set, thefixed telephone set, and the ordinary telephone set as mentionedpreviously in the Definitions of Terms, and hence has the subscriberinformation memory MEM therefor. The second class exchange is connectedto a plurality of first class exchanges via transmission lines as shownand is provided with the subscriber information memory MEM.Higher-ranking exchanges each have also the subscriber informationmemory MEM as depicted. The subscriber information memories provided inthe respective ranks are operatively associated with one another forhandling the request for the registration of the position of theportable telephone set and its charging information, and has adecentralized memory function which is also characteristic of thepresent invention.

(2) The Principle of the Present Invention and the Grounds therefor

This section will describe first that the decentralized arrangement ofthe subscriber information memories in the exchanges of respective ranksis superior over the centralized arrangement used in the prior art, andthen a method of providing the personal identification information PID.

A description will be given first of the function of the subscriberinformation memory (MEM).

(2-1) Function of the Subscriber Information (Information such asPosition Registration and Charging Information for Each PID) MemoryProvided in the Exchange of Each Rank

i) The exchange stores, in the subscriber information memory, subscriberinformation received from the portable telephone set via the key serviceunit, a PBX, or the like, and if necessary, transfers the information tothe higher- or lower-ranking station.

ii) When receiving new subscriber information from the portabletelephone set owing to its movement from the previous place to a newone, the exchange compares the new information with the previous one andrewrites or cancels the stored information, and if necessary, transfersthe new subscriber information to a higher- or lower-ranking exchange.

iii) Where the following subscriber information (1) and (2) have beenprestored for the portable telephone set, even if the exchange receivesthe position register request signal from the portable telephone set, itperforms the registration of the position of the portable telephone setand outgoing and incoming call control therefor in accordance with theprestored subscriber information.

(1) Rejection of the Acceptance of the Position Register Request

The exchange does not register the position of the portable telephoneset, and hence inhibits outgoing and incoming calls. In this case, theexchange notifies a higher- or (and) lower-ranking exchanges of therejection of the registration of the position of the portable telephoneset.

(2) Limited Acceptance of the Position Register Request

In order to control of outgoing and incoming calls of the portabletelephone set, the exchange accepts the position register request withina limited range. (That is, the length of time for an outgoing orincoming call is limited, and the time is limited during which outgoingand incoming calls are permitted in a day.)

iv) Where the fixed telephone set corresponding to the portabletelephone set stays in the home area of the latter, the exchangeperforms an absence transfer service.

v) In case of abnormal communication traffic the exchange performs theconnection of the communication circuit according to the class.

vi) The exchange identifies the method and kind of the registration ofthe position of the portable telephone set, and in the case of anincoming call, determines the method of calling (wide area calling andnarrow area calling)

vi) The exchange transmits to a third party a required portion of theinformation stored in the special information memory for eachsubscriber, on the basis of contracts made with the subscriber and thethird party.

viii) Where the portable telephone set is capable of outgoing andincoming calls of different media services, the state of communicationis stored for each different media.

ix) Data on the telephone rate chargeable on the portable telephone sethaving made an outgoing call in the roam area is acquired by the firstclass exchange to which the portable telephone set belongs, but thecharging data is transmitted via another exchange or the like to thesubscriber information memory of the first class exchange whichadministers the home area of the portable telephone set.

x) Information obtained in the subscriber information memory of theexchange of each rank is transmitted to the wide area portable telephonecalling n-th radio base station which has an interface with theexchange.

(2-2) Function of the Subscriber Information Memory of the Telephone KeyService Unit

i) The PID of the portable telephone set which has acquired the downcontrol signal from the portable telephone key service unit (SID_(n))and requested the resistration of its position is stored in the PIDsignal memory of the key service unit. The portable telephone keyservice unit (SID_(n)) notifies the associated fixed telephone set andKTC-I that the portable telephone set has its position registered in thekey service unit.

ii) In the case where the radio wave field strength of the input to theportable telephone set engaged in communication through the associatedkey service unit has been reduced below a certain level because theportable telephone set has been brought far away from the key serviceunit, the system proceeds to an in-communication channel switchingso-called hand-off operation. The key service unit stores the PID of theportable telephone set in the PID signal memory for a certain period oftime after the channel switching operation. This is intended to providefor re-establishing a communication channel between the key service unitand the portable telephone set in a case where the system has failed theabove channel switching operation.

iii) In the case of communication with the portable telephone set aswell, the key service unit notifies the subscriber information memory ofthe first class exchange of the times of commencement and completion ofthe communication as well as the PID information of the key service unitand the portable telephone set.

(2-3) Function of the Subscriber Information Memory of the FixedTelephone Set

i) This memory stores outgoing call information from the fixed telephoneset and, if necessary, supplies information to the display, and besides,transfers the stored contents in response to a request signal fromKTC-I.

ii) Where the portable telephone set stays in the roam area and does notreceive an incoming call thereto, the memory stores incoming callinformation transferred at certain timing.

iii) Where the portable telephone set has registered its position in theroam area, the memory receives the information from KTC-I-1 and storesit if the necessary function has been preset.

(2-4) Function of the Subscriber Information Memory of the PortableTelephone Set

i) The memory stores the information on the registration of the positionof the portable telephone set in the roam area and outgoing callinformation of the portable telephone set.

ii) The memory stores incoming call information of the portabletelephone set in the roam area.

iii) The self-ID memory stores the self-ID information, a code number,credit information, and other ID information necessary foridentification use.

Moreover, the fixed telephone set responds to a request signal fromKTC-I to transmit thereto required pieces of the information stored inthe self-ID memory above has clarified the functions of the subscriberinformation memories. A description will be given first of the radiocommunication circuit control system for use in the present inventionand then the registration of the position of the portable telephone setwhich plays an important role in the present invention.

The control system for the radio communication circuit between theportable key service unit and the portable telephone set usually employsa plurality of control channels (although only one channel is used as inthe case of the residential district), providing a function ofcontrolling outgoing and incoming calls in a plurality of communicationchannels. The control channels are utilized for the position registerrequest signal from the portable telephone set and a special signal (anoutgoing call stop signal, for instance) to the portable telephone set.However, the present invention is applicable as well to a system inwhich control and communication channels are not separated from eachother as mentioned above. In such a case, the same channel is used firstfor controlling operations of outgoing and incoming calls and then usedas a communication channel. Where the system has a plurality of radiocommunication circuits, a function is provided which retrieve thecommunication circuits in a repeating cyclic order to find an unusedradio communication circuit.

Now, a description will be given of the method of arrangement of controlchannels in the cordless telephone mode, that is, a method of providinga system which permits a number of portable telephone sets toindividually make an outgoing call and receive an incoming call withoutinterference and jamming in the case where a number of portabletelephone key service units are installed in the service area. At first,an example of the system in a residential district, i.e. a portabletelephone control system in the residential district mode will bedescribed. In this instance, the down control channel from each portabletelephone key service unit usually sends out a control signal only whennecessary.

Upon turning ON of the power source of the portable telephone keyservice unit SID₁, it sends out a down ward control signal through downward channel of a predetermined control channel (No. 1, for example) tothe neighboring portable telephone set PID₁ to inform it of the turningON of the power source. The downward control signal contains the SID₁information, the channel number, etc. The portable telephone key serviceunit SID₁ repeatedly transmits the signal of the same contents. At thesame time, the key service unit actuates a signal receiving circuit ofan up channel of the control channel (No. 1) in preparation forreceiving a position registration signal from the neighboring portabletelephone set. In this case, there is installed another portabletelephone key service unit in the neighborhood of the above-mentionedone. Since they employ the same control channel, if their power sourcesare turned ON at the same time, interference and jamming will occur, theprobability of which is very low.

This will hereinbelow be described in concrete numeric values. Assumingthat the number of control channels used is one, the probability ofcontention for the control channel (that is, in the case where theneighboring portable telephone key service units accept positionregister request signals at the time, the signals are not sufficientlytransmitted due to jamming) is 3%, the time for which the controlchannel is occupied by each signal is 10 seconds, the busy hour callconcentration ratio is 1/10, and the number of repetitive zones is 25(that is, all radio waves of the 24 neighboring zones cause jamming),the number N of portable telephone key service units (for each zone)which can be accommodated in the system is given by the followingequation: ##EQU1## where a (1, 0.03) is offered traffic (in Erlang.) onthe condition that the number of outgoing channel is one and thepropagation of lost call is 0.03.

The above shows that about four portable telephne key service units canbe accommodated at a maximum in each zone in which a single key serviceunit usually suffices. It will be appreciated from comparison with acalculated example of the communication traffic in Tokyo, describedlater, that the above value satisfies a necessary condition for theportable telephone system of the residential district mode. Since it isconsidered that the portable telephone key service units are normallyused with their power sources held ON in practice, the above-mentionedvalue may be considered as a condition for setting up the system.Accordingly, the 10 seconds assumed above as the time for which thecontrol channel is occupied by each signal is applied to the time ofestablishing the system. In the case where each portable telephone keyservice units is held with the power source ON, control of outgoing andincoming calls between it and the portable telephone associatedtherewith and other purposes can be achieved within one second.

Next, a description will be given of the number of portable telephonesets which can be accommodated, in view of the control ability of theportable telephone key service unit which is held in the residentialdistrict mode of operation. Assuming, as the conditions of the systemdesign, as in the above, that the control signal disable (owing tointerference) ratio is 3%, the time for which the control channel isoccupied by each signal is 0.5 sec., the busy hour call concentrationratio is 1/10, the number of control operations for outgoing andincoming calls is 10 per day, and the number of repetitive zones is 25,the number n of portable telephone sets which can be accommodated in thekey service unit is given by the following equation: ##EQU2##

That is, about nine portable telephone set can be accommodated. On theother hand, in the case of the residential district mode, one portabletelephone key service unit is installed for each residence and is usedby its all family members. It is considered that the family usuallyconsists of four or less, and even if the number of third parties whowill use the key service unit on roads or similar places outside theresidence is assumed to be four; therefore, the above numerical value isgreater than a total of eight users, and hence does not pose any problemin the system configuration. However, the portable telephone set in thecontinuous position register request mode was excluded from thecalculation. (In practice, since other key service units are installedon posts and at public places in the residential district as well, thenumber of users per key service unit will be further reduced.)

Moreover, the portable telephone system of the residential district modemust be studied from the viewpoint of the communication traffic.Assuming, as the conditions for the system design in this case, that theloss probability is 0.03%, the number of communication channels is 50(in Japan 89 channels will be permitted to use in the end of 1987 forcordless telephone instead 46 channels presently available, the numberof communications is 10 per day, the time for which the control channelis occupied is three minites per call, the busy hour call concentrationrate is 1/10, and the number of repetitive zones is 25, the number m ofportable telephone sets which can be accommodated in each key serviceunit is given by the following equation: ##EQU3##

That is, about 34 portable telephone sets can be accommodated per keyservice unit. As compared with a calculated example of the traffic in 23wards of Tokyo, described later, the above numerical value is sufficientfor dealing with the traffic density in practice.

Next, a description will be given of the communication between theportable telephone key service unit with its power source held ON andthe nearby portable telephone set (in an area in which radio waves aretransmitted well and the communication therebetween is possible). It isconsidered that the neighboring portable telephone set assumes eitherone of the following states:

(1) The portable telephone set was put in the stand-by state (the powersource was turned ON) before the power source of the key service unit isturned ON).

(2) The portable telephone set is put in the stand-by state after thekey service unit was started its operation (the power source was turnedON).

The state (1) will be described first.

In this case, the portable telephone set PID₁ is in the state in whichit is about to acquire (i.e. receive) either one of the down controlchannel of the portable telephone key service unit and the down controlchannel of the wide area portable telephone calling i-th class basestation by cyclically switching them. The length of the control signalfrom the key service unit is made longer than the switching interval andthe portable telephone set PID₁ can well receive this control signalwithout fail. In the case of the portable telephone set in thecontinuous position register request mode, since the position registerrequest mode is received by the key service unit, the positionregistering operation is further ensured.

In this way, the portable telephone set PID₁ receives the down controlsignal from the key service unit SID₁, checks its contents, stores theSID₁ information and other information in its memory, and at the sametime, sends out the position register request signal to the key serviceunit SID₁. The subsequent operations follows the steps described later,completing the registration of the position of the portable telephoneset PID₁. Thereafter, only when an outgoing call from the portabletelephone set PID₁ or an incoming call thereto occurs, the key serviceunit sends out a control signal.

It is seen from the above that in the portable telephone system of theresidential district mode one control channel is sufficient in terms ofthe traffic of the control signal for outgoing and incoming calls. Table1 shows, by way of example, the numbers of various control channelsincluding the above. The reason for which two channels are assigned ascontrol channels in the residential district mode is to cope with anincrease in the communication traffic by the introduction of a newservice or the division of the system; however, one channel will sufficein practice. The portable telephone system of the residential districtmode utilizes frequency more effectively and consumes less power fortransmission than the portable telephone system of the business districtmode. However, in the case where it is desirable to locate the currentposition of, for example, a doctor or salesman as well as communicatewith them through use of this system, it is necessary that the portabletelephone set take the initiative in communication. This demand can bemet by the use of a method in which the portable telephone set put inthe continuous position register request mode sends out the positionregister signal at certain intervals. That is, the continuous positionregister request signal generator and the timer in FIG. 4A are actuatedto operate the controller at, for example, 10- or 30-second, or 1-minuteintervals, sending out the position register signal through apredetermined up control channel, for example, channel 1.

                                      TABLE 1                                     __________________________________________________________________________    Examples of Number and Function of Control Channels                           from Fixed Radio Station in Portable Telephone System                                                 Communication Channel Number                                                          For Both of                                                           For     Communication                                                         Communication                                                                         and Data                                      Kind of Mode                                                                             Control Channel Number                                                                     Only    Transmission                                                                          Note                                  __________________________________________________________________________    Cordless   1  For residential           Control channel                       Telephone     district mode             can be converted                                 2  (transmit when            to communication                                    necessary)                channel.                                         3  For business                                                               4  district                                                                   .  (transmit at                                                               .  all times)                                                                 .                                                                             31                                                                            32                                                                                         33                                                                            34                                                                            .                                                                             .                                                                             .                                                                             150                                                                                   151                                                                           .                                                                             .                                                                             .                                                                             200                                           1st Class Wide Area                                                                         1001˜1020                                                                         --      --      All transmit                          2nd Class Wide Area                                                                         2001˜2121                                                                         --      --      continuously and                      3rd Class Wide Area                                                                         3001˜3121                                                                         --      --      capable of sending                    4th Class Wide Area                                                                         4001˜4020                                                                         --      --      out voice, data,                      5th Class Wide Area                                                                         5001˜5020                                                                         --      --      etc.                                  __________________________________________________________________________

Next, a description will be given of the case where a portable telephoneset PID₂ has entered from the roam area into an area in which it cancommunicate with the portable telephone key service unit SID₁ (the case(2)). In the case where the power source of the portable telephone setPID₁ is turned ON in the neighborhood of the key service unit SID₁, theportable telephone set performs substantially the same operations asdescribed above; therefore, no description will be given thereof, andlet it be assumed that the portable telephone set PID₂ has entered thearea, with its power source held ON. Since the portable telephone setPID₂ usually uses the upward control channel only when necessary andsince the key service unit SID₁ also uses the downward control channelonly when necessary, an outgoing call from the portable telephone setPID₂ can be made (In this case the portable telephone registers itsposition first and then sends out a calling signal.), but an incomingcall can be received only in the wide area calling mode. To avoid this,it is necessary that, as described previously, the portable telephoneset be put in the continuous position register request mode and causedto send out the position register request signal through the controlchannel No.1 at certain time intervals, and that the portable telephonekey service unit having received the signal check its contents, store itin the memory if the portable telephone set PID₂ has not been storedtherein yet, and send out a position registration signal of SID₁ +PID₂to KTC-I.

Incidentally, the communication traffic is sometimes high in the steadystate in connection with a specific area or portable telephone keyservice unit even in the residential district--for example, thecommunication traffic in a supermarket or private store in theresidential district. The communication traffic increases especiallywhen the portable telephone set is used as a credit terminal. To copewith such a situation, the portable telephone key service unit isprovided with a circuit for measuring the communication traffic in thekey service unit itself, as indicated by 1-11 in FIG. 4B. When thetraffic exceeds a certain value, the above circuit provides a stateequivalent to that caused by connecting the switch SW1-10 to the contactS₂, thereby switching the key service unit from the control signalas-required-transmit mode to the control signal normally-transmit mode.This make it possible to cope with an increase in the traffic. When thecommunication traffic becomes smaller than a fixed value, the controlsignal transmission mode is switched from the normally-transmit mode tothe as-required-transmit one, by which it is possible to achieveeffective utilization of frequency and power saving.

Next, a description will be given of a method of switching the portabletelephone system from the residential district mode to the businessdistrict one.

The communication traffic in the residential district is normally smalland substantially uniform over the entire service area, but it sometimesabnormally increases in a specific section when an unexpected accidentoccurs or a meeting or special event is held. A monitor MON included inKTC-I shown in FIG. 5A monitors the comminication traffic in the areawhich the exchange administers, and when the traffic exceeds a certainvalue, the monitor changes the control signal transmission mode in theservice area concerned. In this instance, the residential district modeis switched to the business district one. That is, the mode oftransmission of the control signal from the portable telephone keyservice unit is switched from the as-required-transmit mode to thenormally-transmit one. To this end, a switching signal is transmitted toall portable telephone key service units in the area concerned. The modeswitching section in FIG. 4B has a function of switching between a stateS₁ (the residential district mode) and a state S₂ (the business districtmode) in response to an instruction from the KTC-I. This change of stateis informed to the controller of each key service unit, switching thedown control signal transmission mode from the as-required-transmit modeto the normally-transmit one.

With a view to preventing interference with the down control signal fromthe neighboring key service unit at the time of this change of state,the control channel is also changed (namely, the control channel fromeach portable telephone key service unit is made different from thecontrol channel of the nearby key service unit). As a result of this,the portable telephone system enters the business district modedescribed in detail hereinbelow, making it possible to cope with anincrease in the communication traffic.

Next, a description will be given of the radio communication circuitcontrol system which is employed in the portable telephone system of thebusiness district mode. The method of use of the control channel differsfrom that in the case of the residential district mode described above;namely, the down control channel of each portable telephone key serviceunit sends out the control signal at all times.

The transmission of the control signal at all times, herein mentioned,includes the case of sending out the control signal for one second atregular intervals (or at irregular intervals), for example, at 10-secondintervals. The provision of such a 9-second non-transmission time servesfor the purposes of reducing the power consumption by the transmitter ofeach key service unit and alleviating interference and such anintermittent transmission produces exactly the same effect as isobtainable with the constant transmission, and hence can be included inthe former. In this case, the following three methods are employed forselecting the control channel which is used by the portable telephonekey service unit. Although in this case the number of transmittable andreceivable channels of the portable telephone key service unit isassumed to be one, an example of a plurality of such channels will bedescribed later.

(1) The portable telephone key service unit is equipped with a functionof retrieving down control channels from a number of key service unitsinstalled in its vicinity and selecting a control channel which will notinterfere with those of the other key service units.

(2) Radio control equipment (RC) (see FIG. 5D or 5G) is provided, bywhich are specified the down control channels to be emitted from anumber of portable telephone key service units (SID) subordinate to it.In this case, the radio control equipment RC is equipped with a functionof administering the control channel and a function by which when theportable telephone key service unit, with which the portable telephoneset has communicated, is changed to a new key service unit as a resultof a travel of the portable telephone set from one place to another, thechannel between them is switched to a new one. However, the radiocontrol equipment RC is not permitted to carry out an administrationsuch as specifying the communication channel which is used by eachportable telephone key service unit.

(3) Radio control equipment RC is provided as in the case (2), and isequipped as well with the function of the administration of thecommunication channel.

Now the method (1) will be described first. Let it be assumed that theportable telephone key service in their service areas are each installedat the center of one of such uniformly distributed regular hexagons asshown in FIG. 5I (the service area of each key service unit being ahexagonal zone (each side about 25 m long)). In practice, however,houses differ in size and the key service units are installed atdifferent places within them and hence are not distributed uniformly asshown. In such a case, it is necessary only to avoid interference andjamming by increasing the number of control channels used; therefore,the above assumption will not impose any limitations on the effect ofthe present invention. Numerals in FIG. 5I indicate respective hexagonalzones. Assume that at a certain point of time the portable telephone keyservice units, each disposed in one of zones 1 to 25, are held withtheir power sources in the OFF state, that is, the key service units arenot emitting radio waves. Further, assume that the number of controlchannels is 25. When the power source of the portable telephone keyservice unit in the zone 13 is turned ON at the next point of time, thekey service unit sends out a control signal, using any one of controlchannels (down) Nos. 1 to 25. Prior to the emission of radio waves, thekey service unit sweeps the control channels Nos. 1 through 25 by itsreceiver to check which channel or channels are being used or are notbeing used by any other key service units. In this example, the keyservice unit of the zone 13 finds out that no control channels are notused by the key service units of the other remaining zones. Accordingly,the key service unit of the zone 13 recognizes that any control channelwill not be subjected to interference and jamming. Now, let it beassumed, for convenience of explanation, that the key service unit ofthe zone 13 uses the control channel No. 13.

When the power source of the portable telephone key service unit in thezone 14 is turned ON next, the key service unit will also emit radiowaves through some other control channel after sweeping, by itsreceiver, the control channels Nos. 1 to 25 to check which channel orchannels are being used. In this example, since the control channel No.13 is being used, the key service unit in the zone 13 will use any oneof the other control channels. Let it be assumed, for convenience ofexplanation, that the key service unit in the zones 14 uses the controlchannel No. 14.

Thereafter, when the power sources of the portable telephone key serviceunits in the other zones 1, 2, 3, . . . 12, 15, 16, . . . 24 and 25 areturned ON one after another, the key service unit in each zone performs,prior to the emission of radio waves, the same operation as describedabove, that is, the key service unit checks the control channels No. 1to 25, by sweeping them with its receiver, for an unused controlchannel. In this example, each key service unit recognizes that thecontrol channels of the same number as the zone number of its own is notbeing used, and sends a control signal therethrough.

The zones 1 through 25 in the above description from a part of the wholeservice area as shown in FIG. 5I, in which there are provided zones 26through 50 on the right-hand side of them. As regards the controlchannels to be used in these zones 26 to 50, let it be assumed that eachzone uses a control channel the number of which is equal to the valueobtained by subtracting 25 from its zone number, namely, the controlchannels Nos. 1, 2, 3, . . . are used in the zones 26, 27, 28, . . . ,respectively. Accordingly, the control channel No. 1 is used in thezones 1 and 26. In this instance, the zones 1 and 26 are appreciabledistant from each other, and the control signals from the both keyservice units are attenuated, in terms of their propagationcharacteristic, to such as extent that they will not interfere with eachother. (Incidentally, 12 zones or so are employed in the NTT land mobileradio telephone system.) Accordingly, the use of 25 control channelswill ensure that the control signals from the respective portabletelephone key service units, even if transmitted at the same time, arefree from interference and jamming by the others over the entire servicearea, no matter how wide it may be. Therefore, the system mentionedabove is a kind of cellular system.

Although in the above the portable telephone key service units aredistributed uniformly throughout the service area as depicted in FIG.5I, there is also a case where they are distributed nonuniformly. Insuch a case, it is necessary only to increase the number of controlchannels used. When the relative distance between the portable telephonekey service units which employ the same control channel is smaller thanin the case of FIG. 5I, the introduction of another control channels,for instance, No. 26 will suffice. It is considered that a larger numberof spare control channels may be required in practice. Table 1 showsexamples of the number of control channels and the number ofcommunication channels which are employed in the portable telephonesystem of the present invention. Of the control channels shown in thetable, 30 control channels Nos. 3 to 32 are of the cordless telephonemode.

While in the above the number of the control channel used in each zoneis described to the same as the zone number, this is not alwaysnecessary and it is a matter of course that each zone can use anychannel so long as it does not interfere with other channels.

Moreover, the control channel being used may sometimes be jammed owingto a change in the state of propagation of radio waves or by an externalradio waves even if the control channel is free from such interferenceor jamming at a certain point of time. The portable telephone set andthe key service unit of the present invention are equipped with afunction of checking for such interference and jamming and switching thecontrol channel to another one when recognizing the interference. Forexample, if the control channel being used in the zone 14 is jammed,then another unused control channel, for instance, No. 26 is selectedand used. The same is true of the communication channel. A transmissionquality monitor incorporated in the receiving section of the portabletelephone key service unit always monitors the transmission quality ofthe communication channel assigned thereto and switches thecommunication channel to another one if interference or jamming occurs.

Next, a description will be given of the operation of the portabletelephone key service unit for registering the position of the portabletelephone set. Assume that the portable telephone key service unit(SID₁) is installed in the zone 1 in FIG. 5I and that the power sourceof the portable telephone set PID₁ using this zone as its home area isturned ON. The receiving frequency synthesizer in the portable telephonein FIG. 4A starts its operation, automatically triggering the sweep ofthe control channels Nos. 1 through 32. As a result of this, it acquiresthe control channel in which a downward control signal is flowing. Thedownward control signal contains the SID₁ information, the controlchannel number, etc. Having received the down control signal, theportable telephone set PID₁ provides a position register request signalon the corresponding upward control channel of the control channelNo. 1. This request signal contains the PID₁ information, the channelnumber, etc. Having received this request signal, the key service unitstores the PID₁ signal in its subscriber information memory and, at thesame time, notifies the first class exchange of the position registerrequest from the portable telephone set PID₁. This signal contains PID₁+PID₁ information. Having received this signal, the first class exchangeKTC-I-1 stores in the position registration information memory of itssubscriber information memory that the position of the portabletelephone set PID₁ has been registered in the key service unit SID₁. Atthe same time the first class exchange notifies the key service unitSID₁ that the registration of the position of the portable telephone setPID₁ has been completed. Then the key service unit SID₁ checks thecontents of the signal from the first class exchange and notifies theportable telephone set PID₁ of the completion of the registration of itsposition through the downward control channel.

In this way, the position of the portable telephone set PID₁ in the keyservice unit SID₁ is registered. The above operation is shown in FIG.11A.

Next, a description will be given of an outgoing call from the portabletelephone set the position of which has already been registered. Whenthe portable telephone set PID₁ is off-hooked, it transmits a callrequest signal to the associated key service unit through thecorresponding up control channel of the control channel being acquired.The request signal contains the PID₁ signal. Upon receiving the requestsignal, the portable telephone key service unit SID₁ checks the PID₁signal and then notifies the portable telephone set PID₁ of the numberof the communication channel which is not being used in theneighborhood, asking to send out a dial signal through this channel.(According to the system configuration, the dial signal may betransmitted using the control channel instead of the communicationchannel.) The portable telephone key service unit is capable of storing,by its synthesizer, communication channels which are not always used inits vicinity. That is, if channels 51 and 151 are unused channels amongcommunication channels 33 to 150 and 151 to 200 of the cordlesstelephone mode in Table 1, the channel 51 is used exclusively forcommunication and the channel 151 is assigned to data communication.Accordingly, when receiving the downward control signal appointing thechannel, the portable telephone set actuates its synthesizer underinstructions of the controller, providing the dial signal on thecommunication channel No. 51 or 151.

Thereafter, the call originating operation proceeds in the mannerdescribed later (see FIG. 7A).

The channels Nos. 51 to 200 in Table 1 are used exclusively forcommunication. In a case where the communication traffic has increasedand all the communication channels are busy, no extra channel can beused as a communication channel but the portable telephone key serviceunit possesses a function of provisionally diverting a control channelto communication. If the portable telephone set PID₁ transmits the callrequest signal when the communication channels are all busy, the keyservice unit sends to the portable telephone set PID₁ a command signalinstructing it to use the control channel No. 11 as a communicationchannel. Then the portable telephone set PID₁ sends out the dial signal,using the control channel No. 11 as a communication channel accordingly.After this, the call originating operation proceeds as depicted in FIG.7A.

Next, a description will be given of the number N of portable telephonesets which can be accommodated in terms of the processing capability inthe portable telephone system of the business district mode describedabove. Using, as various numerical values for calculation, the samevalues used previously for the residential district mode (except thatthe communication traffic is 40 times per day), the number N is given asfollows: ##EQU4## That is, 56 portable telephone sets can beaccommodated in each zone. It was assumed, however, that the number ofrepetitive zones need not be taken into account since adjoining zonesuse different control channels.

Judging from the above, it is possible to implement a system modeldescribed later.

Next, a description will be given of a radio communication circuitcontrol method of the portable telephones of the business district modeat a place congested with people.

It is considered that even if the afore-mentioned portable telephonesystem of the business district mode is applied at such a place, nosatisfactory communication can be achieved because of high trafficdensity. A solution to this problem is the adoptation of smaller zones.In the above the service zone of one portable telephone key service unitis selected to be a zone with a radius of 25 m, but if the transmittingpowers of the portable telephone set and the key service unit andreduced and if the radius of the service area of the latter is reducedto 10 m, then (25/10)² =6.25; this represents a six-fold or moreincrease in the communication traffic that can be processed. From thetechnical point of view, this can easily be done, for example, byreducing the transmitting power of the key service unit to 1 mW which is1/10 of its ordinary transmitting power and by furnishing the portabletelephone set with a transmitting power control function by which itresponds to the down control signal to lower its transmitting power tothe same level as that of the key service unit only when it is used inthe small zone. This is a known technology.

A second solution is to instal a plurality of portable telephone keyservice units in the same service zone (cellular zone). By employing nkey service units in the service zone, the traffic processing capabilityin that zone will become n-fold. However, this calls for n control andcommunication channels for each zone and hence is not so advisable buteconomical. A more effective method will be described below.

According to this third method, the radio communication circuit controlequipment RC mentioned previously in (2) (see FIG. 5D) is utilized, bywhich are appointed down control channels from a number portabletelephone key service units placed under control of the equipment RC. Inthis instance, however, the function of the radio communication circuitequipment RC is limited to the administration of the control channelsand the switching of the channel of the portable telephone set duringcommunication. Further, this method is applied to the portable telephonesystem of the business district mode because the function of theequipment RC is not performed in the residential district mode.

With the provision of the radio communication circuit control equipmentRC, it is possible to assign the control channels to its subordinateportable telephone key service units under a certain rule or utilize,for the channel assignment, values of interference and jammingpremeasured in a state in which control signals were actuallytransmitted from a number of key service units. Therefore, this methodimproves the utilization efficiency of frequency as compared with thecase described previously in (1). FIG. 5J shows an example of thismethod, in which the number of repetitive zones is 12; accordingly, thesame frequency can be reused for every 12 zones. Also in this case,however, it is better to prepare a spare channel against the occurrenceof interference or jamming, and it is possible to instal two portabletelephone key service units for each small zone in anticipation of anincrease in the traffic density of the whole system. In such a case, thenumber of control channels is 12×2=24 plus the spare channel.

With the use of this method, the portable telephone key service unit foruse in the residential mode can be utilized as it is, with no particularnecessity of newly designing the key service unit. However, this methodemploys two control channels for each zone, and hence is notadvantageous from the viewpoint of efficient utilization of frequency.To avoid this shortcoming, it is also possible to employ a method inwhich one control channel is assigned to each zone and is caused tocontrol the use of a plurality of communication channels, as shown inFIG. 5K Since the number N of portable telephone key service units whichcan be accommodated in one zone in terms of the control signalprocessing capability is 4.45 as referred previously, four to five keyservice units can be provided in this method. Also in this case, it ispossible, of course, to divert the transceiver for the control channeluse to communication in the case of a traffic congestion. (The controlsignal used in this case is outside the band of the communicationsignal.)

It is considered that this method (2) will be used in many cases whenthe portable telephone system is extended. The method (1) is simple insystem configuration, and hence is suitable for use in an area of smallcommunication traffic, such as a residential district. On the otherhand, the method (2) will be employed in an area of large traffic, suchas busy streets. However, the method (2) will be used as well in theresidential district when the communication traffic therein increases.

The registration of the position of the portable telephone and itscalling operation are carried out in the same manner as described above.FIG. 5G shows the case where the radio communication circuit controllerRC is disposed apart from the exchange KTC-I, but they may also beprovided at the same place. Alternatively, it is possible to dispose oneradio communication circuit controller in each administrative district,i.e. in each town and each village, and place the controllers RC underthe same exchange KTC-I.

In the radio communication circuit controller RC shown in FIG. 5G, acontrol channel controller is capable of applying a control signal to acommunication channel controller, instructing it to switch thecommunication channel in response to the travel of the portabletelephone unit or for avoiding interference and jamming.

Now, the method (3) will be described. FIG. 5H shows an embodiment ofthis method, in which the communication channel as well as the controlchannel are designated by the radio communication circuit controller RC.This method is of particular utility when employed in an area ofextremely high traffic.

The above has described the communication circuit control of theportable telephone systems of the residential district mode and thebusiness district mode. Next, a description will be given of theoperation of the portable telephone near the boundary between areas inwhich these two modes are employed, respectively.

Now, let be assumed that a portable telephone owner is walking near theboundary between the above-mentioned areas, with his portable telephoneset PID₁ held in the ON state. In such a situation, the portabletelephone set usually tries to acquire the down control channel, andhence is considered to belong to the business district mode. As he walksaway from a business district and into a residential district, the SNratio of the control channel acquired until then becomes deteriorated.When the SN ratio becomes smaller than a certain value, the portabletelephone set proceeds to the retrieval of another down control channel.In this case, however, the portable telephone set cannot acquire anydown control channel because in the portable telephone system of theresidential district mode no key service unit sends out the down controlchannel at all times. After a certain elapsed time the portabletelephone set decides that it has entered the residential district modearea, and thereafter sends out a position register request signalthrough an up channel of a control channel (channel No. 1 is Table 1)assigned under the portable telephone system of the residential districtmode. Upon receiving this request signal, the nearest portable telephonekey service unit in the residential district mode registers the positionof the portable telephone in the same manner as described previously,after which the portable telephone set operates in the residentialdistrict mode. Where the portable telephone set was initially set in thecontinuous position register request mode, it will return to its initialstate and resume the continuous transmission of the position registerrequest signal.

In the case where a portable telephone set in the residential districtmode has been carried in the business mode area, if the portabletelephone set is in the continuous position register request mode, it iscontinuously transmitting its PID₁ signal through the up control channelof the channel No. 1 shown in Table 1. In this case, however, since theportable telephone set has entered the business district mode, it cannotreceive any answer through the down channel of the control channel No. 1from the portable telephone key service unit in the residential districtmode area. Then, after a certain elapsed time the portable telephone setautomatically stops the continuous signal transmission for theregistration of its position and starts searching for a down controlchannel which is used in the business district mode. That is, theportable telephone set cyclically retrieves the control channels Nos. 3to 32 of the cordless telephone mode shown in Table 1. Thus the portabletelephone set acquires an unused control channel and then proceeds toits stand-by state.

Even in the case where the portable telephone set has succeeded inacquiring the down control channel of the cordless telephone mode, if itstill continues travelling, its down control channel receiving powerdecreases, and finally the received signal quality also falls below acertain transmission quality standard. Then the portable telephone setgives up the down control channel and resumes the retrieval to catchanother down control channel, thereafter repeating exactly the sameoperations as described above.

The above is the case in which the portable telephone set is in thecontinuous position register request mode. Next, a description will begiven of a portable telephone set which is in the ordinary residentialdistrict mode.

In this instance, the portable telephone set still remains in the stateof receiving the down control signal in the channel No. 1 shown in Table1 even after it has entered the service area of the business districtmode. Accordingly, the portable telephone set cannot receive an incomingcall and cannot but resort to the wide area calling mode therefor. Asregards an outgoing call, the portable telephone set transmits a callingsignal through the up channel of the control channel No. 1 in Table 1but receives no answer from the nearest portable telephone key serviceunit; and so that after a certain elapsed time the portable telephoneset automatically starts the retrieval of a down control channel whichis used in the business distric mode.

Therefore, the subsequent operations are exactly the same as describedpreviously.

In order to enable the portable telephone set of the present inventionto communicate with other telephone sets at all times even while itsowner travels all over the country, it is necessary to always detect thecurrent position of the portable telephone set, that is, monitor andstore with which key service unit the portable telephone set is able tocommunicate. This is done by the subscriber information memories (MEM)of the portable telephone key service unit and the first to fifth classexchanges.

The registration of the position of the portable telephone set isclassified into the following six cases according to the distance fromits home area.

In the following it is assumed, for the sake of brevity, that theportable telephone system of the business district mode is used in whichthe portable telephone key service unit always transmits a controlsignal through a down control channel. In the case of the residentialdistrict mode, since the key service unit does not send out the controlsignal at all times, the portable telephone set must be switched to thecontinuous position register request mode when it transmits the positionregister signal to the key service unit, but the subsequent operationsare identical with those in the normally-transmit mode.

i) Position Registration in the Home Area

Upon turning ON the power source of the portable telephone set in itshome area, it immediately starts the operation for registering itsposition. FIG. 11A shows the flow of operation in this case. Thefollowing description will be given with reference to FIG. 11A. In FIG.11A, when its power switch is turned ON, the portable telephone set PID₁acquires a down control cahnnel of the portable telephone key serviceunit SID₁ in the home area and transmits thereto a position registerrequest signal, using the corresponding up control channel. The portabletelephone key service unit SID₁ receives and stores the request signalin its memory and at the same time transmits it to the first classexchange KTC-I-1. The exchange KTC-I-1 stores in its subscriberinformation memory that the position of the portable telephone set PID₁has been registered in the key service unit SID₁ of its home area, afterwhich the exchange transmits a registration completion signal to theportable telephone key service unit SID₁. When receiving the signal, thekey service unit SID₁ collates the PID₁ information contained in thesignal and then transmits a registration completion signal to theportable telephone set PID₁, which, in turn, checks the signal contentsand stores the SID₁ information.

Thus the registration of the position of the portable telephone in thehome area is completed.

ii) Position Registration in the First Class Roam Area

Referring next to FIG. 11B, the position registration in the first classroam area will be described. In FIG. 11B, when its power source isturned ON, the portable telephone set PID₁ transmits a position registerrequest signal to the associated portable telephone key service unitSID₁ as in the above. Upon receiving the request signal, the key serviceunit SID₂ checks the PID₁ information contained in the received signal.In this case, the key service unit SID₂ recognizes that the portabletelephone set PID₁ is not a portable telephone set PID₂ associated withthe key service unit but a portable telephone set of a third party inthe roam area. Then the key service unit SID₂ stores the PID₁information in its memory and transmits a position register requestsignal to the exchange KTC-I-1. The exchange stores in its memory thatthe position of the portable telephone set PID₁ has been registered inthe key service unit SID₂ in place of the key service unit SID₁, andthen transmits a completion signal to the key service unit SID₂. Thesubsequent operations are exactly the same as those in the case of FIG.11A and the registration of the position of the portable telephone setPID₁ in the key service unit SID₂ is finished.

Next, a description will be given, with reference to FIG. 11C, of theposition registration in the case where the portable telephone set PID₁with its power source held ON has been moved in the first class roamarea. In FIG. 11C, the portable telephone set PID₁ still holds the downcontrol channel from the portable telephone key service unit SID₂, butas it travels, its input radio wave field strength decreases and finallybecomes lower than a fixed reference value. Then the portable telephoneset PID₁ starts the retrieval of another control channel on the basis ofinformation from a noise level detector (see FIG. 4(a)). When theportable telephone set PID₁ finds that the input field value of a downcontrol channel from another portable telephone key service unit, forexample, SID₃ satisfies the reference value, the portable telephone setPID₁ rewrites the SID₂ information prestored in its memory to the SID₃information, and transmits a position register request signal to the keyservice unit SID₃. The key service unit SID₃ stores the PID₂ informationin its memory and transmits a position register request signal to theexchange KTC-I-1. The subsequent operations are the same as in the caseof FIG. 11B.

iii) Position Resistration in the Second Class Roam Area

With reference to FIG. 11D, the operation flow in this case will bedescribed. In FIG. 11D the operations from the turning ON of the powersource of the portable telephone set PID₁ to the signal reception by anexchange KTC-I-2 are exactly the same as those in the case of FIG. 11D.Having checked the contents of the position register request signal, theexchange KCT-I-2 recognizes that the portable telephone set PID₁ is nota portable telephone set which the exchange administers, and stores thePID₁ information in its position registration memory. At the same timethe exchange KTC-I-2 transmits a position register request signal to anexchange KTC-II-1 which administers the portable telephone set PID₁.After checking the contents of the request signal, the exchange KTC-II-1stores the signal in its position registration memory and requests theexchange KTC-I-1, which administers the portable telephone set PID₁, tostore that the position of the portable telephone set PID₁ has beenregistered in a portable telephone key service unit SID₄ which theexchange KTC-I-2 administers. The exchange KTC-I-1 checks the contentsof the request signal, stores it in its position registration memory,and further transmits a registration completion signal to the exchangeKTC-II-1. The exchange KTC-II-1 collates the contents stored in itsposition registration memory and then transmits a registrationcompletion signal to the exchange KTC-I-2. The subsequent operations areexactly the same as in the case of FIG. 11C and the registration of theposition of the portable telephone set PID₁ in the portable telephonekey service unit SID₄ is completed.

i) Position Registration in the Third Class Roam Area

Turning next to FIG. 11E, the operation flow in this case will bedescribed. In the operation flow of position registration shown in FIG.11E the operations from the turning ON of the power source of theportable telephone set PID₁ to the signal transmission to an exchangeKTC-II-3 are exactly the same as those in the case of FIG. 11D.

A position register request signal transmitted to the exchange KTC-II-3is checked and stored in its memory. Since it is found, as a result ofthis checking, that the portable telephone set PID₁ is not a portabletelephone set which the exchange administers, the exchange KTC-II-3transmits a position register request signal to a high-ranking exchangeKTC-III-1. The exchange KTC-III-1 recognizes that the portable telephoneset PID₁ is under its control, and stores the signal in its memory.Further, the exchange KTC-III-1 transmits a position register requestsignal to the exchange KTC-II-1. The subsequent operation followsexactly the same process as in the case of FIG. 11D, completing theregistration of the position of the portable telephone set PID₁ in aportable telephone key service unit SID₅.

v) Position Registration in the Fourth Class Roam Area

FIG. 11F shows the operation flow in this case. This operation flow isexactly identical with that in FIG. 11E except the intervention of thefourth class exchange.

vi) Position Registration in the Fifth Class Roam Area

FIG. 11G shows the operation flow in this case. This operation flow isexactly identical with that in FIG. 11F except the intervention of thefifth class exchange.

Incidentally, it is not always necessary to store the positionregistration information of the portable telephone set PID₁ in thememories of the exchanges KTC-II-3 in FIG. 11E, KTC-II-4 and KTC-III-4in FIG. 11F, and KTC-II-5, KTC-III-5 and KTC-IV-5 in FIG. 11G. Even ifthe information is not stored in the memories of these exchanges, theeffect of the present invention will not be adversely affected at all.However, by such a seemingly awkward operation of storing the positionregistration information in each exchange it is possible to obtain theadvantage that when the portable telephone set PID₁ in a certain roamarea is called from a roam area of the same kind, a channel can beestablished between them simply by retrieving the exchange whichadministers the latter roam area, without the need of inquiring of ahigher-ranking exchange. Judging from the fact that memories are nowbecoming more and more inexpensive, it is preferable to store theregistration information in the memories of all exchanges which takepart in the registration.

Finally, the operation for cancelling (or transferring) the registrationwill be described in connection with the case where the portabletelephone set PID₁ having been registered in the fifth class roam areanow transfers the registraction of its position to the home area.

vii) Operation by which Portable Telephone Set PID₁ Registered in FifthClass Roam Area Transfers its Position Registration to Home Area

As a matter of fact, a situation like this would arise, for example, inthe case where a person who lives in Tokyo travels to Hokkaido carryinga portable telephone set with him, uses it at various places inHokkaido, holds it OFF on his way home, and then turns it ON in his homeon the following day.

In this instance, the portable telephone set registers again itsposition in its home area in Tokyo through the following flow ofoperation, which is exactly reverse from that for the positionregistration in the fifth class roam area described above with regard toFIG. 11G. That is, the exchanges SID₁, KTC-n-5 (where n=1, 2, 3, 4, 5)and KTC-n-1 (where n=1, 2, 3, 4, 5) have stored in their memories thatthe position of the portable telephone set PID₁ is registered in anexchange SID₇, but this information is changed (or erased). In concreteterms, the exchange SID₁ changes in its memory the registration of theposition of the portable telephone set in the fifth class roam area tothe registration in the home area. The exchange notifies the exchangeKTC-I-1 that the portable telephone set PID₁ has requested to registerits position. The exchange KTC-I-1 retrieves its memory and changes thestored contents and, at the same time, request the exchange KTC-II-1 tochange (or erase) the registration of the position of the portabletelephone set PID₁. The exchange KTC-II-1, in turn, erases the positionregistration information of the portable telephone set PID₁ stored inits memory and requests the exchange KTC-III-1 to change (or erase) theposition registration information of the portable telephone set PID₁.Thus the position registration information of the portable telephone setPID₁ stored in the memories of all the exchanges except those SID₁ andKTC-I-1 is erased.

The above has clarified the operation for registering the position ofthe portable telephone set. As described above, the registration of theposition of the portable telephone set is always carried out in theportable telephone system of the present invention. In addition, thethus registered position is limited to an area with a radius of 25 m inthe cordless telephone mode, and hence is very accurate. Accordingly, inthe case of supervising the current positions of insurance canvassers orsalesmen through use of an electric scoreboard or similar equipmentinstalled in their office or the like, the purpose can easily beattained simply by letting them carry portable telephone sets with themand receiving their registered position information from the nearestfirst class exchange (KTC-I-1). As will be appreciated from the above,the present invention is of very wide application includingcommunication.

In order to make full use of the position registration in the portabletelephone system of the present invention, it is a precondition that theportable telephone be held in the stand-by state (with its power sourceON). Taking into account the fact that the power consumption of ICs andhigh-frequency circuits are now being reduced more and more, it isdesirable that the portable telephone set having once left the home areabe held in the ON state. If portable telephone sets in the roam areasatisfy this condition, then the following new services can be achieved.

(1) Each portable telephone owner can send out an emergency call incases of a tidal wave, a typhoon, some other calamities, and accidents.

(2) Even if an important person who has not registered his portabletelephone set for some reason, he can be called up in the wide areacalling mode (using a satellite).

(3) It is possible to communicate with a salesman, doctor, or some otherperson who has arrived at a designated city, town, or village.Conversely, when such a person has left a certain area, he canautomatically inform his office in the home area that the registrationof the position of the portable telephone has been changed.

(4) A service of reporting market conditions at the fixed time every daycan be performed for persons who are travelling all over the country.

(5) An emergency message from the portable telephone set can effectivelyexecuted.

Next, the application of this invention system to the above cases willbe concretely described in detail.

(a) Emergency Call from the Owner of the Portable Telephone Set

It is predetermined, in this case, that when the owner of the portabletelephone set feels ill or is suddenly taken ill in his home orsomewhere else, he needs only to press an emergency call button of theportable telephone set or dial "119" (an emergency number now adopted inJapan). When receiving the emergency call, an emergency medical centercan dispatch an ambulance to the place where the patient is, immediatelyafter making the exchange KTC-I-1 transfer information about the currentposition of the portable telephone set. In the existing system for theaged, old men and women are each given what is called an emergencypendant and when this pendant is pulled in case of emergency, radiotransmitter incorporated therein sends out an SOS call to an emergencymedical center which is ready to dispatch an ambulance at all times. Thepresent invention will enhance the performance of this system andextends its service area across the country. Similarly, in a case of afire at the place where the owner of the portable telephone set is, heneeds only to say "fire" after dialing "119", for example (the verbalmessage is not always needed but may be substituted with a dial signalor the like), without the necessity of telling the place name andaddress of the scene of the fire and explaining in detail appearances ofthe neighboring buildings as in the existing system. In a fire defensecenter the registered position of the calling party can be displayed onits electric scoreboard, and accordingly, fire engines can immediatelydispatched to the scene of the fire.

Also in a case of a crime or traffic accident, by dialing "110", forinstance, from the portable telephone set at the scene, its currentposition can clearly be recognized at a squad car control center, andaccordingly, effective activities can be performed.

(b) Current Position Sending of a Senile Person, etc.

At present the Japanese population is aging and the number of elderlypeople is on the increase; at the same time, an increasing number ofsenile persons is becoming a social problem. In particular, senilepersons who slip out of their homes and wander about aimlessly day andnight are annoyance to the neighborhood and are likely to meet trafficaccidents; and so that members of their families are mentally exhaustedby searching for their missing old people. The portable telephone systemof the present invention is good news as well to the families who havesenile persons on their hands.

Letting such a senile person carry a portable telephone set (with itspower source held in the ON state) with him, it is very easy to find himsimply by inquiring the current position of the portable telephone setfrom the exchange KTC-I-1. In a similar manner, letting a child get holdof a portable telephone set in a spacious pleasure ground, for example,he can easily be found even if he should get lost.

While the above description has been given on the assumption that thesubscriber information memory of the n-th class exchange has a storagecapacity large enough to store new information at all times, thesituation arises where it cannot store the positional information of theportable telephone set PID because of the saturation of its storagecapacity or its breakdown. In this case, the positional information isstored by other exchanges in the order of their priorities. Where thesubscriber information memory of the n-th class exchange becomes out oforder, the (n+1)th class exchange stores the information. If thisexchange cannot store the information, then the information istransferred to a higher class exchange and finally to the fifth classexchange. When the memory of the fifth class exchange cannot store theinformation either, the position of the portable telephone set PID isregistered in the portable telephone key service unit or fixed telephoneset (SID₁) of the home area.

When an incoming call to the portable telephone set PID₁ is made in theabove-said state, its current position is inquired of the exchange SID₁through a transmission line, after which the portable telephone setPID.sub. is called through the exchange which administers the area inwhich the portable telephone set PID₁ is staying actually. Thuscommunication is enabled between the calling and called parties withoutany trouble although the control signal makes an appreciably longdetour.

It will be appreciated from the above how important a role thesubscriber information memory of the n-th class (where n=1, 2, 3, 4 and5) plays in the system of the present invention. Now a description willbe given of the traffic which uses this memory and its required storagecapacity, showing that the decentralized system of the present inventionis advantageous over the conventional centralized system.

(2-5) Position Registration Traffic and Required Storage Capacity

The portable telephone set of the present invention is carried tovarious places all over the country and is used for outgoing calls toand incoming calls from telephone sets at various places. Accordingly,the current position of the portable telephone set must always beregistered each time it has moved from one place to another, so as tomake it ready for communication with other telephone sets at all times.The system of the present invention calls for such constant registrationof the current position of the portable telephone set but is far moreefficient, economical and rational than the prior art systems, asdescribed below in detail.

Roughly speaking, users of portable telephone sets in Japan (or theJapanese people in general) stay at home or at their places ofemployment almost all day, and accordingly they go out at acorrespondingly low frequency. In addition, the time for and thefrequency at which they go out markedly decreases in inverse proportionto an increase in the distance to the destination of visit.

For example, an average office worker spends business hours almost athis desk and even if he leaves his seat, he does not go so far away but,at most, calls at a council room, another working room or so in the samebuilding. Even if he carries his portable telephone set with him on suchan occasion, he needs only to change the positional informationregistered in the subscriber information memory of the PBX or firstclass exchange. This can be done by the signal transmission andreception between the portable telephone set, the key service unit, andthe PBX (or first class exchange) only.

Even if a company employee is ordered to go on business, it is usually ahalf-day's or a day's trip. As viewed in terms of the class of exchangeused in the present invention, almost all business trips are within thesame city (the service area of the second class example) and the sameprefecture (the service area of the third class exchange). There areonly slight chances of a business trip to a place outside the prefecture(the service area of the fourth exchange) and a long-distance businesstrip, for example, from Tokyo to Hokkaido (the service area of the fifthclass exchange).

The above is not necessarily limited to office workers alone. Forinstance, an ordinary housewife also stays at home almost all day long,usually except going out for shopping or making an errand in theneighborhood of her home. That is, the scope of her daily activity islimited to the city or prefecture where she lives. Usually she willseldom go to other prefectures.

Moreover, the frequency at which the whole family goes out forrecreation or some other purposes is very low as described later.

From the above it will be understood that the frequency of using thesubscriber information memories (the registered position Memories) ofhigh-ranking exchanges, that is, the frequency of the signaltransmission for registering the position of the portable telephone setis very low. Accordingly, from the viewpoint of the national traits ofthe Japanese people it is considered to be most suitable to employ thedecentralized registration system for registering the position of theportable telephone set each time it moves from one place to another.

It can be said that the present invention entirely differs in this verypoint from the prior art which administers subscriber informationcentralized at only one place.

Now, daily activities of the Japanese people in general, such asmentioned above, will be described in detail by reference to aliterature (Investigative Report on the Movement of Travellers in Japan,edited by the Prime Minister's Office, October 1982). That is, thetraffic densities at which portable telephone owners are registered inthe first to fifth class exchanges will hereinbelow be calculated on thebasis of the Report.

a) Kind, experience rate and number of travels

In twelve months from September 1980 to August 1981, 66.0% of theJapanese people experienced an overnight trip or two or more day'strips. (Table 2)

                  TABLE 2                                                         ______________________________________                                        Experience rate and average number of                                         travels according to the kind of travel                                       Kind              Experience rate                                                                            Average                                        ______________________________________                                        *Sightseeing tours                                                                              45.9%        0.821  times                                   Business trips    7.1          0.180                                          *Business trips combined with                                                                   4.2          0.060                                          sightseeing                                                                   Trips for family and private                                                                    9.1          0.139                                          reasons                                                                       Homecoming        13.8         0.235                                          *Trips for family and private                                                                   9.5          0.126                                          resons and homecoming                                                         combined with sightseeing                                                     Schooling         3.6          0.044                                          *Schooling combined with                                                                        2.2          0.023                                          sightseeing                                                                   Others            3.4          0.044                                          Unknown purpose   0.6          0.010                                          Total of all travels                                                                            66.0         1.683                                          *Total of sightseeing and                                                                       53.3         1.030                                          sightseeing combined with                                                     others                                                                        ______________________________________                                    

                                      TABLE 3                                     __________________________________________________________________________    Inter-block movement                                                          (Movement rate initiating on departure basis according to places of           departure)                                                                    NTT                                                                           area       To                                                                 Dial                          Hokuriku.                                       number                                                                             From  Hokkaido                                                                           Tohoku                                                                             Kanto                                                                             (Tokyo)                                                                            Koshinetsu                                                                          Tokai                                                                             Kinki                                                                             Chugoku                                                                            Shikoku                                                                            Kyushu                                                                             Total              __________________________________________________________________________    01   Hokkaido                                                                            85.9 5.5  2.1 (0.7)                                                                              --    1.4 2.4 1.0  --   1.7  100                02   Tohoku                                                                              3.1  71.4 11.0                                                                              (6.4)                                                                              4.6   3.9 4.6 0.2  0.2  1.0  100                04   Kanto 1.9  5.0  39.6                                                                              (2.9)                                                                              20.1  24.5                                                                              4.6 0.8  0.5  1.4  100                03   *(Tokyo)                                                                            (1.2)                                                                              (4.1)                                                                              (40.9)                                                                            (4.2)                                                                              (24.7)                                                                              (22.4)                                                                            (4.5)                                                                             (1.0)                                                                              (0.3)                                                                              (0.8)                                                                              100                07   Hokuriku.                                                                           0.6  7.2  13.8                                                                              (6.4)                                                                              49.8  13.8                                                                              11.7                                                                              0.2  2.3  0.6  100                     Koshinetsu                                                               05   Tokai 1.0  0.9  6.2 (2.5)                                                                              28.9  42.9                                                                              15.9                                                                              1.8  1.2  1.3  100                06   Kinki 2.0  0.6  2.6 (1.3)                                                                              21.0  15.0                                                                              43.6                                                                              8.6  3.0  3.6  100                08   Chugoku                                                                             1.0  0.5  3.9 (2.6)                                                                              2.3   1.8 25.6                                                                              36.8 9.1  18.9 100                08   Shikoku                                                                             --   --   2.6 --   2.6   5.1 33.3                                                                              10.2 38.5 7.7  100                09   Kyushu                                                                              1.2  2.0  1.6 (1.0)                                                                              0.8   1.0 6.7 6.9  2.4  77.6 100                __________________________________________________________________________     *Tokyo is a part of Kanto and these figures are picked up from Kanto.    

The experience rate of overnight, two or more day's trips is 45.9% forsightseeing, 7.1% for business, 13.8% for homecoming, 9.1% for familyand private reasons, etc. Adding up the experience rates of the tour forsightseeing alone and the tour for sightseeing and other purposes, theexperience rate is 53.3%.

The number of times of overnight or few day's trips is 1.683 on average;0.821 times for sightseeing only and this is 48.8% of the total number.The number of times of business trips is 0.180 and the number of timesof homecoming journeys is 0.235. The total of the numbers of times ofpure sightseeing tours and sightseeing tours combined with some otherpurposes is 1.030 and accounts for 61.2%.

The annual per capita total number of travelling days is 4.92 days onaverage.

b) Movement between blocks

Looking at the destinations of visits from places of departure in eachblock, the rate of intra-block trips is high in every block, as shown inTable 3.

c) Foreign tours

The per capita rate of experience of travelling abroad from September1980 to August 1981 is 2.0%. The number of days of travelling abroad foreach traveller in the above-said period is 8.6 days on average.

d) Day trip for sightseeing and recreation

The results of questionnaires on day trips for sightseeing andrecreation, conducted in two months January and February and in twomonth of July and August 1981, shows that the experience rate per eachfamily is 32.4% in winter and 43.6% in summer; the latter exceeds theformer by 10 points. The mean number of day trips for each person is0.659 in winter and 0.956 in summer.

Classifying day trips for sightseeing and recreation by destination,i.e. inside and outside the administrative divisions (of Japan) whererespondents to the questionnaires lived, more than 60% of therespondents went on days trips in the administrative divisions of theirown in both winter and summer.

(2-6) Estimation of Traffic for Position Registration and StorageCapacity of the Subscriber Information Memory of Each Exchange

a) Fifth class exchange

Where a Japanese wants to use his portable telephone set whiletravelling abroad, he must register the position of the portabletelephone set in the memory of this exchange.

Since each Japanese makes a trip 0.03 times per year and the averagenumber of days therefor is 8.6, the rate at which each Japaneseregisters the position of his portable telephone set in the fifth classexchange in a year is as follows:

    0.03 times×8.6 days=0.248 day-times/person-year

That is, where the traffic is uniform, even if 80% (one hundred million)of all the Japanese (one hundred one twenty million) possess portabletelephone sets, the required storage capacity of the fifth classexchange is as follows: ##EQU5## That is, a storage capacity for 70,000persons will suffice.

Moreover, it is necessary to take into consideration that the positionof each portable telephone sets is registered when it moves from onefourth class roam area to another. This corresponds to the case where aportable telephone subscriber who lives in Tokyo, for example, makes atrip to Hokkaido. The number of such position registrations can beobtained from the following equation on the basis of Table 2. ##EQU6##This shows that each portable telephone subscriber annually uses thememory for 3.87 days while travelling to areas outside the areas of hisown.

Further, since he travels 1.2 times per year, and since it is consideredthat he seldom visits a plurality of districts in one travel, he willuse the memory for 0.66×4.92=3.2 days. Therefore, the traffic forregistration is 1.2 times×2=2.4 times (for registration and erasing).

From the above, the annual traffic and storage capacity of the fifthclass exchange necessary for position registrations of each portabletelephone set during overseas and out-of-district tours is as follows:

    Traffic: (0.03+1.2)×2=2.46

Storage capacity: 0.248×3.873=4.116 day-times That is, each portabletelephone set annually accesses the fifth class exchange 2.5 times anduses it 4.12 days ##EQU7## Therefore, the total storage capacity is for1130,000 persons ##EQU8## In the above, the traffic which uses the widearea calling fifth class radio base station of the present invention andthe storage capacity therefore were neglected because their estimationsare difficult and because the actual traffic is considered small.

b) Fourth class exchange

It is necessary to add intra-block movement, such as the Tokyo or Tohokublock in Table 3, and the movement by day trips.

As for the former, the number of accesses by each portable telephone setfor each year is:

    0.4903 times×0.66×4.92 days=1.592 day-times

As for the latter, the estimated result of similar calculation will be1.456 day-times.

In addition, since the fourth class exchange also operates upon eachoccurrence of registration in the fifth class exchange, this must betaken into account as follows: That is, each portable telephone setaccesses the fourth class exchange 6.35 times and uses its memory for7.16 days for each year.

c) Third class exchange, etc.

It is difficult to estimate the traffic and the storage capacities ofthe third to first class exchanges because they are greatly affected bythe manner in which subscribers use their portable telephone sets. Asregards the storage capacities, however, these exchanges will have to bedesigned taking into account that each portable telephone set will usethe third, second and first class exchanges for 20 to 30 days, 50 to 100days, and 365 days annually. The ground for the above calculations arethe results of investigations conducted in 1980 as mentioned in theaforementioned literature. The above estimated values will have to besomewhat corrected in accordance with changes in the lifestyle of thepeople. Yet, it is believed that there will be no substantial changewhich disproves the basis of the present invention radically.

In the above, rough estimations were made of the traffic which uses thesubscriber information memories and their required storage capacities inthe present invention. Next, a rough estimation will be made of therequired traffic and storage capacity in the case of employing theafore-mentioned functions and operations and the conventionalcentralized memory system (in which the subscriber information memory isprovided at one place alone).

(1) Traffic

The traffic becomes enormous since position registration information,charging information, etc. must be transmitted to the single memorywhenever portable telephone sets each have moved from one place toanother, as described previously in i) to iii). In particular, thecharging information is transmitted immediately after on-hooking of eachportable telephone set (If not, other memories are needed and the effectof the centralized memory system is not produced.), so that thetransmission of the charging information takes place in the busy hourduring which the communication traffic is congested, and the capacity ofthe communication circuit must be increased accordingly. In contrastthereto, according to the present invention, the charging informationneed not be transmitted immediately after the end of communication butneeds only to be transmitted to the exchange KTC-I once a day, week, ormonth, and besides, it is possible to select therefor a time slot ofsmall traffic at night, for example. Accordingly, the decentralizedmemory system of the present invention is advantageous over theconventional centralized memory system in this regard as well.

(2) Memory capacity

Comparing the decentralized subscriber information memory system of thepresent invention and the conventional centralized memory system, it isapparent that the storage capacity needed in the former is smaller thanin the latter. This will be discussed below quantitatively. In orderthat the centralized memory system may provide the same service as thatof the present invention, it is necessary to place the subscriberinformation memory in a telephone station corresponding to the firstclass exchange (for storing charging information, for example);therefore, the point is the difference between the storage capacities ofthe second to fifth class exchanges in the present invention and thememory capacity of the centralized memory. Since the storage capacitiesof the fifth and fourth class exchanges are very small, the storagecapacities of the second and third class exchanges and the storagecapacity of the centralized memory must be compared. The storagecapacity required in the decentralized system is larger than the storagecapacity (M₀) of the centralized system by ##EQU9## where M₂ and M₃ arethe total storage capacities of the second and third class exchangesdistributed all over the country. The actual values of M₂ and M₃ differaccording to the design concept employed, that is, depending upon themargin technique for the busy hour, but the above value is estimated torange from 2 to 3.

In recent year, however, since hardware for use in memories has becomemore and more lowcost, the larger storage capacity of this inventionsystem is not a serious demerit; rather, the superiority in terms oftraffic is important.

(3) PID (Personal Identification Information)

Next, a description will be given of a method of appending PIDinformation to each portable telephone set in the present invention.

Information which is contained in the PID enables the followingidentification:

(1) Identification of a particular person in distinction of the otherpersons. (That is, even in the same family its members are never giventhe same PID information.)

(2) Identification of each of the first to fifth class roam areas. (Thisis the most striking feature of the PID appending method of the presentinvention.)

(3) Clear indication of the position of the home area of each portabletelephone set, i.e. the address of the portable telephone subscriber(that is, the place where he is). (What is intended to mean by the"clear indication" is not that the PID information enables the user toimmediately know the position of the portable telephone set, but thatwhere there is stored in, for example, the subscriber information memoryof a first class exchange a contrastive table showing PID information ofportable telephone sets whose first class roam areas belong to theservice area of this exchange and the names of places where they are,the address of a particular portable telephone subscriber can easily beobtained from his PID information stored in the memory of this firstclass exchange.) Moreover, when a plurality of home areas areregistered, priorities must be assigned to them.

(4) Identification of the regional center, the district center, tollcenter, and terminal station to which the portable set PID belongs to,and besides, the corresponding ward, town (address). This is requiredfor the reason given above in (2).

(5) Identification of the administrative division, city (ward), ward andtown (address) to which the portable telephone set stays. This isrequired for the reason given above in (3).

(6) Identification of countries (in anticipation of future extension ofthe system)

(7) Identification of service class

(8) Permitting the appending of a code number to the portable telephoneset for preventing it from theft and from being used by a third partywithout leave.

(9) Identification of the following service classes

i) Limiting the area in which an outgoing or incoming call is possible

ii) Limiting the hour and minute for an outgoing or incoming call

iii) Limiting the time slot for an outgoing or incoming call

iv) Indicating whether an additional service, such as a conferencesystem, is available

v) Indicating where or not a fixed telephone set corresponding to theportable telephones set exists in its home area

vi) Connecting a communication circuit for each class in case ofabnormal traffic

vii) Indicating whether or not the portable telephone system is combinedwith another mobile communication system

viii) Indicating whether a non-telephone (non-voice) service isavailable

ix) Permitting the general calling of a plurality of portable telephonesets appended with the PID information under a specific rule

A description will be given first of the number of digits necessary forthe PID information, followed by the PID configuration for use in thepresent invention.

Since Japan has a population of about 120,000,000, it is necessary toidentify this number. If what is called a national number system isadopted, then nine digits will suffice as follows:

    xx-xxx-xxxx (where x=0, 1, 2, . . . 9)

However, since it is necessary to satisfy the requirements mentionedabove in (1) to (9), the nine digits will be insufficient. Then, thefollowing number of digits are assigned to each of the following areas.

Fifth class roam area: three digits for country xxx (country ID)

Fourth class roam area: two digits for administrative division xx(administrative division ID)

Third class roam area: Three digits for city ward (in the case of Tokyo)or country xxx (city ID)

Second class roam area: Three digits for ward, town or equivalent place(city of less than 50,000 being partly included) xxx (town ID)

First class roam area: four digits for address, name of housing complexor name of apartment house xxxx (subscriber ID)

That is, a total of 13 digits are required. Furthermore, seven digitsare needed for the service class, VIP identification and a code number.Accordingly, a total of 20 digits are necessary, and the number of bitsinvolved is 4×20=80 bits. However, the identification of country willnot be required for the time being. In principle the calling party neednot dial the service class, the VIP identification, and the code number.FIG. 6 shows the PID appending method described above.

In practice, since it is necessary, for improving the service of thesystem, to assign each subscriber the PID information of the smallestpossible number of digits, the number of digits at the time ofintroduction of this system will be reduced to substantially the samenumber as the NTT's national number. However, the following descriptionwill be made on the basis of the number of digits shown in FIG. 6, so asto explain the feature of the present invention.

The portable telephone subscriber of the system of the present inventioncan originate an outgoing call at any place all over the country ofJapan and can also receive an incoming call from any place all over thecountry. The PID appending method of the present invention produces itseffect in the case of an incoming call. Now, let it be assumed, forexample, that Mr. A whose home area is Hoya-shi, Tokyo is travelling allover the country, and that Mr. B, a friend of Mr. A, who lives inKumamoto in Kyushu, wishes to call Mr. A, using an ordinary telephoneset. The flow of signals of the incoming call will be described inconnection with the cases where Mr. A is in the first to fifth classroam areas, respectively.

[1] In the case of the first class roam area:

Mr. B dials the PID signal (from which the code number and the serviceclass are omitted in FIG. 6) of Mr. A. In this case, it is necessary todial all pieces of Mr. A's PID information, that is, the administrativedivision ID, the city ID, town ID, and the subscriber ID. If Mr. B'stelephone set is under control of the same n-th class exchange as Mr.A's portable telephone set, Mr. B needs only to dial the followingidentification information:

    n=1: subscriber ID

    n=2: town ID+subscriber ID

    n=3: city ID+subscriber ID

    n=4: administrative division ID+city ID+town ID+subscriber ID

Even if the town ID or city ID is dialled despite of n=1, the exchangejudges and hence does not connect the call errouneously or make itimpossible of connection; accordingly, the desired incoming calloperation can be performed. After receiving the call signal from Mr. B,the first class exchange which administers his telephone set starts arouting operation for establishing a channel between Messrs. A and B. Atfirst the exchange starts to send out a control signal for retrievingthe positional information of Mr. A. After recognizing from Mr. A's PIDinformation that Mr. A's portable telephone set is administered by theexchange KTC-I in Hoya-shi, Tokyo, Mr. B sends out an outgoing call(control) signal to higher-randing exchanges sequentially whichadminister Mr. A's telephone set; finally the call signal reaches thesubscriber information memory of the fifth class exchange.

Then, the subscriber information memory is retrieved, but since theposition of Mr. A's portable telephone set has not been registered inits fifth class roam area, an incoming call (control) signal istransferred to the fourth class exchange (KTC-IV-1) which administersMr. A's portable telephone set. The subscriber information memory of thefourth class exchange is also retrieved, but since it has not registeredthe position of Mr. A's portable telephone set in the fourth class areaeither, the incoming call signal is further transferred to the thirdclass exchange, for retrieving its subscriber information memory. Now,let it be assumed that since it has been found that the position of Mr.A's portable telephone set in the roam area was not registered in theexchanges from the fifth to first class one (KTC-I-1), the incoming callsignal is transferred to the first class exchange (KTC-I-1) as is thecase with an incoming call to an ordinary telephone set, and it has nowfound, as a result of the memory of the first class exchange, that Mr.A's portable telephone set is not in the home area but has its positionregistered in a roam area key service unit SID₂.

This positional information is sent back to the calling-side exchangeKTC-I in a direction exactly reverse from the direction of flow of thesignal described above, that is, via a route [KTC-I-1 - KTC-II-1 -KTC-III-1. In the case of sending back Mr. A's positional information,however, the exchanges KTC-I-1, KTC-II-1, . . . KTC-IV, KTC-V, KTC-VI, .. . KTC-II each append the positional information with initial pathentry in the case of setting a path from the exchange to the callingtelephone set and the called subscriber portable telephone set. Sincethis information is very effective and contains the communicationtraffic state which each exchange seizes at that point of time, thecalling-side exchange can perform optimum routining at that point oftime through utilization of these information. Incidentally, thefollowing routining technique is the same as in a known fixed network.

That is, a channel is set from the exchange which administers Mr. B'stelephone set to the exchange KTC-I-1 which administers Mr. A's portabletelephone set. Namely, it is shown that channels have been establishedfrom the exchange KTC-I to KTC-II and from the exchange KTC-II toKTC-I-1. The exchange KTC-I sends out a ring-back tone to the callingtelephone set, and the exchange KTC-I-1 sends out an audible ringingsignal to the called portable telephone set via the portable telephoneset key service unit SID₂. Thus, the key service unit SID₂ retrieves thePID memory of its own and recognizes that the position of Mr. A'sportable telephone set has been registered, and accordingly, sends outthe incoming call signal to the portable telephone set PID₁. Then, whenMr. A hangs off his portable telephone, his communication with Mr. Bstarts.

The above-described routing method according to the present inventionaims at the most effective use of the network from the viewpoint of thewhole telephone network as well. Accordingly, it is possible to offerhigh-quality services to users and to economically design the network.In the prior art, the routing for setting a communication network isperformed by the calling-side exchange 3 alone, whereas in the presentinvention the routing can be performed by all exchanges which areconcerned in the retrieval or transmission of the registered positionalinformation. This greatly influences the efficient use of the network.The information thus retrieved is added to a signal (14) which isapplied to the exchange KTC-V. Such routing and retrieval are carriedout by each exchange and the results are added to a signal which isapplied to the next exchange. Finally, all the information thus obtainedis provided to the calling exchange KTC-1.

Upon completion of the communication between Messrs. A and B, thechannel established therefor is opened using the same technique as inthe fixed telephone network.

[2] In the case of the second class roam area

In this case, the operations from the transmission of the dial signal byMr. B to the reception of the incoming call signal by the second classexchange (KTC-II-1) which administers Mr. A's portable telephone set arethe same as in the case [1].

Having received the incoming call signal to Mr. A, the second classexchange KTC-II-1 retrieves its memory and, as a result, finds that Mr.A has registered his position and stays in the service area of theexchange KTC-I-2, not in the service area of the exchange KTC-I-1 whichadministers the home area of Mr. A's portable telephone set. Then, theexchange KTC-II-1 transmits the incoming call signal to the exchangeKTC-I-2. The exchange KTC-I-2 retrieves its memory and when itrecognizes that the portable telephone set PID₁ has been registered inthe portable telephone key service unit SID₃ placed under administrationof the exchange KTC-I-2, it sends out the incoming call signal to thekey service unit SID₃. The subsequent operations are the same as in thecase [1].

[3] In the case of the third class roam area

In this case, the operations from the transmission of the dial signal byMr. B to the reception of the incoming call signal by the third classexchange (KTC-III-1) which administers Mr. A's portable telephone setare the same as in the case [1].

Upon transmission thereto of the incoming call signal to Mr. A, thethird class exchange KTC-III-1 retrieves its memory and, as a result,finds that Mr. A has registered his position and stays in the servicearea of the exchange KTC-II-2, not in the service area of the exchangeKTC-II-1 which administers the home area of Mr. A's portable telephoneset. Then, the exchange KTC-III-1 transmits the incoming call signal tothe exchange KTC-II-2. The exchange KTC-II-2 retrieves its memory andwhen it recognizes that the portable telephone set PID₂ has beenregistered in the exchange KTC-I-2 placed under administration of theexchange KTC-II-2, it sends out the incoming call signal to the exchangeKTC-I-2.

Upon receiving the incoming call signal, the exchange KTC-I-2 retrievesits memory and when it recognizes that Mr. A's position has beenregistered in the portable telephone key service unit SID₃, it sends outthe incoming call signal to the key service unit SID₃. The subsequentoperations are the same as in the case [1].

[4] In the case of the fourth class roam area

In this case, the operations from the transmission of the dial signal byMr. B to the reception of the incoming call signal by the fourth classexchange (KTC-IV-1) which administers Mr. A's portable telephone set arethe same as those in the case [1].

Upon transmission thereto of the incoming call signal to Mr. A, thefourth class exchange KTC-IV-1 retrieves its memory and, as a result,finds that Mr. A has registered his position and stays in the servicearea of the exchange KTC-III-2, not in the service area of the exchangeKTC-III-1 which administers the home area of Mr. A's portable telephoneset. Then, the exchange KTC-IV-1 transmits the incoming call signal tothe exchange KTC-III-2. The exchange KTC-III-2 retrieves its memory andwhen it finds that the position of the portable telephone set PID₁ hasbeen registered in the exchange KTC-II-3 placed under administration ofthe exchange KTC-III-2, it sends out the incoming call signal to theexchange KTC-II-3. The subsequent operations are identical with those inthe case where the same operations as in the case [3] are each carriedout by the immediately higher-randing exchange.

[5] In the case of the fifth class roam area

In this case, the operations from the transmission of the dial signal byMr. B to the reception of the incoming call signal by the fifth classexchange KTC-V which administers Mr. A's portable telephone set are thesame as those in the case [1].

Upon transmission thereto of the incoming call signal to Mr. A, thefifth class exchange KTC-V retrieves its memory and, as a result, findsthat Mr. A has registered his position and stays in the service area ofthe exchange KTC-VI-2, not in the service area of the exchange KTC-IV-1which administers the home area of Mr. A's portable telephone set. Thenthe exchange KTC-V transmits the incoming call signal to the exchangeKTC-IV-2. The exchange KTC-IV-2 retrieves its memory and when it findsthat the portable telephone set PID₁ has been registered in the exchangeKTC-III-3 placed under administration of the exchange KTC-V, it sendsout the incoming call signal to the exchange KTC-III-3. The subsequentoperations are identical with those in the case where the sameoperations as in the case [4] are each carried out by the immediatelyhigher-randing exchange.

Next, a description will be made in connection with the case where Mr.A's positional information is not obtained unregistered state) althoughMr. B's call request signal has been handled in any of theabove-described cases [1] to [5].

Technically, it is considered that this state corresponds to one of thefollowing cases:

a) Although Mr. A registered the position of his portable telephone setin the roam area where he stayed, the registration was cancelledaccording to regulations because he did not use the portable telephoneset for a certain period of time after the registration. At present theportable telephone set is not in the ON state or stays in a dead area ofthe cordless telephone mode.

b) The portable telephone set is overlapped by the land mobile radiotelephone mode or some other mobile communication and the positionalinformation was cancelled for some reason.

c) Mr. A carries the portable telephone set with him without registeringits position in the home area (power ON) and, at present, the portabletelephone set is not ON or stays in a dead area of the cordlesstelephone mode.

(In the above cases a) to c), Mr. A's positional information is notavailable. In the following cases, calling takes place at the registeredposition, but since no answer is obtained, the portable telephone isvirtually in the unregistered state.)

d) Mr. A left the service area of the portable telephone key serviceunit in which the position of the portable telephone set was registeredin the portable telephone system of the residential district mode andentered another area of the residential district mode, but no outgoingand incoming operations were carried out for a certain period of timethereafter.

e) Although Mr. A stays at the position registered in the portabletelephone system of the residential district mode or business districtmode, the portable telephone is in the OFF state or cannot receive andincoming call because radio wave propagation is locally poor.

Solutions to the above problem will be described below.

One solution is automatic calling of the fixed telephone set in Mr. A'shome area. In this case, even if Mr. A is absent, it is possible topartly satisfy the caller's requirement by use of an automatic answeringtelephone set or through communication with a member of Mr. A's family.

A second method is to send out a call signal from the wide area portabletelephone set calling i-th class radio base station via the i-th classexchange.

In the respective cases a) to e), the portable telephone set is in theOFF state or the portable telephone set is in the ON state and has itsposition already registered but no outgoing and incoming operations havenot been carried out even after a certain elapsed time. The portabletelephone set has a function of starting an inter-channel sweep foracquiring a down control signal (a control signal which is transmittedfrom the portable telephone key service unit or the wide area portabletelephone set calling i-th radio base station) in these cases.Accordingly, it can be said that the portable telephone set is in thewide area calling mode.

Where an incoming call has occurred to the portable telephone set insuch an unregistered state, its position must be registered beforeeverything else. The method therefor has already been disclosed in ourprior Japanese Patent Application No. 254659/86 "Wide Area PortableTelephone Set Calling System", but routing after the positionregistration which is related directly to the present invention will bedescribed below.

Since the called portable telephone set A has been found unregistered asa result of searching for its position registration in the exchangeKTC-I-1, a call signal is sent out from the wide area portable telephoneset calling first class radio base station via the exchange KTC-I-1.

This method is effective, for example, when Mr. A's sphere of movement,because the first and fourth class radio base stations can be utilized.Let it be assumed, however, that the portable telephone set A isincapable of being called for some reason. This decision is made wherethe called portable telephone set does not answer a certain period oftime after the transmission of the call signal. In this instance, thecontrol signal for routing flows to a higher stage, finally, enters theexchange KTC-V. The exchange KTC-V determines to call from the wide areaportable telephone set calling fifth class radio base station andtransmits thereto a signal. The base station responds to the signal tocall the portable telephone set A, using calling radio waves. Assumethat Mr. A happens to be on the outskirts of Sapporo, Hokkaido and in anunreceivable area more than 100 m away from any of portable telephonekey service units installed in some places on the streets, but that theportable telephone set is in the ON state fortunately and receives theradio waves. At this time, the portable telephone set generates anaudible ringing signal, notifying Mr. A of the incoming call. Thisaudible ringing signal is different in tone from that in the cordlesstelephone mode, so that Mr. A can immediately understand the situation.In this case, a red lamp is lighted in the display of the portabletelephone, indicating that no outgoing call can be made. Then, as Mr. Aapproaches the nearest portable telephone key service unit, a blue lampis lighted instead of the red one. Then, he stands by for a while, withthe call button pressed for sending out an answer signal. When receivingthe answer signal, the nearest portable telephone key service unitchecks the signal content, stores it in its memory and, at the sametime, transmits a PID₁ signal plus the answer signal to the exchangeKTC-I-2.

The exchange KTC-I-2 checks the content of the PID₁ signal and transmitsto the higher-randing exchange the PID₁ signal appended with a signalindicating that the PID₁ signal is an answer signal to the wide areacalling ((22) to (25)). The fifth class exchange, when receiving thesignal, confirms that it is the answer signal from the portabletelephone set PID₁, and transmits Mr. A's positional information to thefirst class exchange KTC-I to which the calling telephone set belongs.It is a matter of course, in this instance, that as in theaforementioned case, the exchanges KTC-I-2, KTC-II-2, . . . KTC-IV-2,KTC-V, KTC-IV, . . . KTC-II, involved in the transfer of Mr. A'spositional information each performs routing therefrom and transmits therouting information as well.

The exchange ITC-I, which has received the routing information and Mr.A's positional information, begins setting up a channel between thecalling party Mr. B and the called party Mr. A. Now, let it be assumed,in this case, that such a channel as shown in FIG. 10C is established inview of the communication traffic at that time. That is, channelsbetween the exchanges are KTC-I→KTC-II→KTC-III→KTC-II-2→KTC-I. Theexchange KTC-I sends a ring-back tone to the calling telephone set B andaudible ringing signals and to the called portable telephone set A, andupon off-hooking of the telephone set B, communication starts. Uponcompletion of the communication, the channel is opened as in the case ofthe known fixed telephone network.

In addition to the above-described wide area portable telephone setcalling function, the present invention has a function of sending outthe communication signal itself to the portable telephone set, usingradio waves from the wide area portable telephone set calling i-th classradio base station. This function provide the following advantages insuch cases as:

i) The service area is in a city or like place and the portabletelephone set cannot sufficiently receive signals from the key serviceunit because of poor radio wave propagation characteristic. But the keyservice unit can sufficiently receive signals from the portabletelephone set because their frequency differs from that of the signalstransmitted from the key service unit or by virtue of the use oftransmission diversity techniques.

This includes the case where the transmitter of the portable telephonekey service unit is incapable of transmission because of trouble.

ii) Where the service area is in an agricultural area far away from acity and communication traffic is very small, the portable key serviceunit is not equipped with a transmitter, for some economical reason orfrom the viewpoint of maintenance, and is installed exclusively forreception use.

In this case, one or more wide area portable telephone set calling firstclass radio base station are installed for each town or village and areconnected to the first class exchange. The first class exchange performswide area calling of the portable telephone set concerned and transmitscommunication information thereto, following instructions from thehigher-randing i-th class exchange. This will hereinbelow be describedin detail.

Also in this case, let it be assumed that Mr. A whose home area wasHoya-shi, Tokyo was making a tour of the whole country and that hisfriend Mr. B, who lived in Kumamoto, Kyushu, wishes to call Mr. A, usingan ordinary telephone set. The flows of the call request signal from Mr.B is are exactly the same as described for the cases [1] to [5]previously. Assume that a call signal for calling Mr. A's portabletelephone set was sent out from the wide area portable telephone setcalling third class radio base station having an interface with thethird class exchange KTC-III-1 (14), and that the call signal wasreceived by the portable telephone set A which was in the area of thiswide area calling service and was held in the ON state.

Since the portable telephone sets generated an audible ringing signal ofa tone peculiar to the wide area calling, Mr. A understood that he wasbeing called by the wide area calling, and found the red lamp ON,indicating that no outgoing call could be made, but Mr. A who happenedto be on the outskirts of a mountain village in Saitama Prefecturepositioned at the outskirt of Tokyo tentatively pressed the call buttonbecause he thought that the communication traffic there would be verysmall and a portable telephone key service unit there might not beequipped with a transmitter. The portable telephone set A sent out acall request signal (an answer signal in this case) and the PID signalcontained in the call request signal was received by the nearestportable telephone key service unit SID₂₀ with no transmitter. The keyservice unit SID₂₀ checked and stored the received signal in its memoryand, at the same time, transmitted the answer signal of the portabletelephone set A to the first class exchange KTC-I-2 which administeredthe key service unit SID₂₀. Since this signal contained the PID₁information of the portable telephone set A, and SID₂₀ signal, andsignals indicating that the received signal was an answer to wide areacalling and that a communication signal would have to be sent out from awide area radio master station because the key service unit SID₂₀ had notransmitter, the exchange KTC-I-2 stored these signals in its memory andtransmitted them and its ID information (KTC-I-2) to the second classexchange which administered the first class exchange. The second classexchange processed the received signal in the same manner as did thefirst class exchange and transmitted the received signal and its IDinformation (KTC-II-2) to the third class exchange (KTC-III-1). As aresult of retrieving its subscriber information memory, the third classexchange recognized that the ID information of the portable telephoneset A contained in the received signal was the ID information of theportable telephone set which had been called from the wide area callingthird class radio base station which has an interface with the thirdclass exchange. Then the third class exchange determined to set achannel and flowed routing control signals to exchanges on the side ofthe calling party in the order ofKTC-IV-1→KTC-V→KTC-IV→KTC-III→KTC-II→KTC-I. The exchange KTC-I applied aring-back tone to the calling telephone set. On the other hand, theexchange KTC-I set a channel KTC-I→KTC-II→KTC-III-1 on the basis of therouting information therefor. Then, on the basis of the routinginformation, the exchange KTC-III-1 decided it would be proper totransmit the incoming call signal, a voice signal, etc. to the calledportable telephone from a wide area portable telephone set calling thirdclass radio master station KRC-III-1 which had an interface with theexchange KTC-III-1. In this case, it would also be possible to transmitthe signals from all radio base stations KRC-III-1, but a channel setrequest signal to the exchange KTC-II-2 from the viewpoint of efficientutilization of frequency. The exchange KTC-II-2 similarly selected frommany wide area portable telephone set calling first class radio basestations KRC-I in its the service area a radio base station KRC-I-2which had an interface with the first class exchange KTC-I-2, and theexchange KTC-II-2 requested the selected radio base station KRC-I-2 tosend out the incoming call signal. However, where only an i-th radiobase station existed and (i-1)th (i-2)th, . . . first class radio basestations were not provided, the communication signal and other signalswould naturally be send out from the i-th radio base station.

The radio base station KRC-I-2 transmitted, by its transmitter, theincoming call signal to the portable telephone set A. The incoming callsignal was confirmed by Mr. A and, by hanging off his portable telephoneset, his voice was sent out therefrom to the portable telephone keyservice unit SID₂₀.

When the calling telephone set B is also hung off, communication isenabled between Mr. A and Mr. B. When the telephone set is hung on uponcompletion of the communication, the above-noted channel B - KTC-1 -KTC-II - KTC-III-1 - KTC-II-2 - KTC-I-2 - SID₂₀ - A is opened naturally.

In the above, it was assumed that the exchange KTC-II-2 is subordinateto the exchange KTC-III-1, but if the portable telephone set is inHokkaido as described previously in connection with FIG. 10C, the formeris not subordinate to the latter. In such a case, the exchange KTC-II-2traces back to the higher-randing exchanges in the order of KTC-III-2 -KTC-IV-2 - KTC-V until the portable telephone set A answers. As a resultof this, the wide area calling and the transmission of the communicationsignal are performed by the radio base station KRC-V or the like on thebasis of the stored information of the called portable telephone set.

Furthermore, the above-described answer signal from the called portabletelephone set need not always be stored in the memories of the keyservice unit SID₂₀ and the exchanges KTC-I-2, KTC-II-2, etc. as far asthis incoming call is concerned. The answer signal is stored onlybecause it will facilitate outgoing or incoming call processing in thefirst class exchange and others when Mr. A will have called anothersubscriber or will have been called by a subscriber other than Mr. B.

Next, a description will be given of other advantages of the PIDassignment to the portable telephone system of the present invention.

(1) Group calling

When administrative authorities want to send administrative informationto residents of the same prefecture, city, town, or village, they needonly to perform general calling for the ID information, shown in FIG. 6,which covers required residents.

(2) Guide service

Since the PID information corresponds to a place name as describedlater, the desired name can be roughly judged simply by checking the PIDinformation.

(3) To use a postal code number as a substitute for the administrativedivision ID, city ID, or like ID

The PID information in the portable telephone system of the presentinvention is classified into the administrative ID, city ID, town ID,and subscriber ID. Accordingly, even if the calling party knows thepostal code number of the subscriber desired to be called (602, forexample), his town ID (123, for example) and his subscriber ID (1234,for example) alone, an outgoing call request can be made. In thisinstance, the first class exchange which has received the call requestsearch its postal code number versus district ID constrastive table forthe telephone number of the called party and dials, for example,#0-602-123-1234 from the portable telephone set of the first classexchange, thereby enabling communication with the called party. That is,the exchange decides, from its constrastive table, that the postal codenumber 602 represents Kamigyo-ku, Kyoto-shi, Kyoto-fu, and converts itto the ID of Kyoto-fu (555, for example) and the city ID (45, forexample).

According to the portable telephone system of the present invention, anysubscriber need not always remember the other party whom he desires tocall. If the calling party knows the address and name of the other partyalone, the exchange KTC-I informs the calling party of the other part'scorrect number as a result of reasoning by AT (Artificial Intelligence)of a number directory of the exchange. For instance, when the callingsubscriber verbally dials "KYOTOSHI KAMIGYOKU SHMOTACHIURI OOMIYAAGARUTANAKACHO 202 BANCHI NOSEHAJIME", he will get an answer "HIS NUMBERIS xxx-xx-xxx-xxxx. DO YOU WANT TO COMMUNICATE?". If the calling partydesires to communicate, he needs only to dial #1 and if not, then dial*2. Thus, the calling party can attain his object. The reason for thisis that reasoning by the artificial intelligence since the PIDinformation is separated into the administrative division ID, city ID,town ID, and subscriber ID.

(4) [Ground on which even if the transmitting power of the portabletelephone set is very low in a city district, communication is enabledall over the district, and an Embodiment]

As regards the prospects for future mobile communications

In Japan, a literature [Long-Term Prospects for Utilization of RadioFrequency Spectrum (edited by Radio Technical Council, published byRadio Promotion Association (a foundation), July 1984] states asfollows: The importance of mobile communications will further increaseand it is expected that there will be a growing demand for itsquantitative enlargement and qualitative improvement. Since no mobilecommunication service can be existent without efficient utilization ofradio frequency spectrum, it will be necessary to strive as hard aspossible for reserving required radio frequency spectrum to meet thedemand for mobile communications.

Accordingly, it is necessary to take measures for enhancing thecapability of accomodating mobile communication subscribers, such asintegration of various systems, development of technologies forefficient utilization of radio frequency spectrum, development of newfrequencies for mobile communications.

There are cases where the following communications are carried out:

(1) Communication with essentially mobile members (man, train, ship,airplane, etc)

(2) Cordless communication utilizing radio frequency spectrum for moreconvenience

The following is a rough estimate of demand which will be in 2000 or sofor each of principal service for which many needs can be anticipatedand which will call for a relatively wide frequency band.

(1) Land mobile radio telephone

4,500,000 (10% of all vehicles)

Tokyo metropolitan area: 1,150,000

(25% of all lend mobile radio telephones)

(2) Portable telephone

1,200,000 (1% of population)

KANTO populated area including Tokyo: 300,000

(25% of all portable telephone sets)

(3) Train public telephone: 1,000

(4) Maritime mobile radio telephone:

50,000 (ships of 5 and more tons)

(5) Maritime satellite communication: 100,000

(6) Aircraft radio telephone: 1,000

(7) Cordless telephone:

7,000,000 (10% of all telephone sets)

KANTO populated area including Tokyo: 1,750,000

(25% of all telephone sets)

(8) Pocket pager:

6,000,000 (5% of population)

KANTO populated area including Tokyo: 1,500,000

(25% of all pocket pagers)

Police, protection against disasters, fire fighting etc.

600,000

Two-way radio for protection against disasters

4,800,000 (4% of population)

KANTO populated area including Tokyo: 1,200,000

(25% of all two-way radio sets)

Personal radio (non-common carriers):

6,000,000 (5% of population)

KANTO populated area including Tokyo: 1,200,000

(25% of all personal radio sets)

Fishery radio: 400,000

As set forth above, it is expected that mobile communications in Japan,especially, land mobile radio telephone will attain a great development.

The present invention concerns the portable telephone in theabove-mentioned mobile communications. The portable telephone hereinmentioned includes all of the mobile communications (1) to (7). FIGS. 5Band 5C show national portable telephone network structures according tothe present invention.

(5) Constitution of Portable Telephone System in 23 Wards of Tokyo asEmbodiment of the Invention

The present invention will be described in detail as being applied to aportable telephone system in a city. FIG. 5B shows the systemconfiguration of the portable telephone system of the present inventioncarried into practice in 23 wards of Tokyo. A description will be givenfirst of the constitution and operation of this invention system in theyear of 2000 when it will come into full use, followed by those of thesystem at an earlier stage of its partial introduction. The former is anultimate form of this invention system, so to speak. At the earlierstage of its partial introduction the system of the present invention isput to use in combination with existing various mobile communicationsystems such cordless telephone, land mobile radio telephone and pocketpager systems. Under such circumstances the portable telephone system ofthe present invention must therefore be designed for use in common tothem. Accordingly, the system configuration at the early stage ofintroduction will naturally somewhat differ from the ultimate one interms of software as well as hardware, but the both systemconfigurations are equally advantageous.

(6) Constitution of National Portable Telephone Network of the PresentInvention

Assuming that the construction of the portable telephone system of thepresent invention will substantially completed in the year of 2000 orso, the final system configuration will be such as shown in FIGS. 5A and5B. Suppose that the first class exchange KTC-I-1 in FIG. 5A accomodatesa portable telephone set (PID₁). The exchange KTC-I-1 accommodates manyother portable telephone sets, portable telephone key service units(SID₁, SID₂, SID₃), and fixed telephone sets, together with ordinarytelephone sets as well, though not shown. (Circles are each a servicearea of one key service unit.) A portable telephone key service unitSID₄ has the same electric characteristics as those of key service unitsinstalled in houses but is disposed on an outdoor post and connected viaa transmission line to the exchange KTC-I-1. Such key service units areprovided at many places on the streets and in other public spaces sothat portable telephone sets can be used at any desired places.Reference numeral 5 in FIG. 5A indicates a large building. Broken-linedcircles are each the service area of one of many portable telephone keyservice units installed in the building so that portable telephone setscan be used at any desired places in the building. These portabletelephone sets and key service units are accommodated in the exchangeKTC-I-1 or KTC-I-2. Reference character MEM attached thereto indicatestheir subscriber information memories. The first class exchanges (localoffices) KTC-I-2 are KTC-I-2 or unshown ones are each connected to ahigher-randing second class exchange (KTC-II-1) as shown. The secondclass exchange (KTC-II-1), is connected to a higher-randing fourth classexchange (KTC-III-1), which is, in turn, connected to a higher-randingfourth class exchange (KTC-IV-1), which is similarly connected to thehighest-randing fifth exchange (KTC-V) as shown. Furthermore, asatellite can also be employed exclusively for calling portabletelephone sets. Thus the portable telephone network spreads all over thecountry. Reference character MEM denotes a subscriber information memoryof each exchange.

In order to allow the portable telephone set of the present invention tooriginate an outgoing call and receive an incoming call at any place,for example, in the 23 wards of Tokyo, about one million key serviceunits will be required; and this is fully realizable as described later.Accordingly, it can be said that in the year of 2000 or so everyportable telephone subscriber will be able to originate an outgoing callto and receive an incoming call from any place not only in cities butalso in agricultural and mountain villages all day and all night.

The above is the cases where the portable telephone subscriber uses hisportable telephone set in building or while walking down the street. Thefollowing will describe outgoing and incoming call operations on a car,ship, train, or airplane and a network configuration and system whichare applied to outgoing and incoming call operations in a place whereradio waves do not propagate well, such as an underground passage orparking lot.

Turning now to FIG. 5B, the parts corresponding to those in FIG. 5A areidentified by the same reference characters and will not be described,but parts different from those in FIG. 5A will be described.

Assume that the portable telephone subscriber has now got into a car,with his portable telephone set held in the ON state. In this case, itis necessary, even in the year of 2000, to put the portable telephoneset in a land mobile radio telephone mode described later for outgoingand incoming call operations; however, the following description will bemade in respect of the case where the portable telephone set is leftunswitched to the land mobile radio telephone mode by mistake or onpurpose. In such an instance, the portable telephone key service unit inthe business district mode is always transmitting the control signal.(There is no such a fear in the portable telephone system in theresidential district mode.) Accordingly, the down control channel beingemitted transmitted from the nearest portable telephone key service uniton a street lamp post can be well received by the portable telephone seteven in the car. Yet, as the car starts running, the portable telephoneset quickly goes away from the key service unit on the street lamp postand finally becomes incapable of receiving the down control channeltherefrom. At this time, however, the car approaches another portabletelephone key service unit and its down control channel out to present areceived radio wave field strength large enough to be received by theportable telephone set in the car. Therefore, the portable telephone settries to store, in its roam area communication information memory, SIDinformation, the number of an idle channel, etc. contained in the downcontrol channel from the key service unit but before this process iscompleted the car runs out of the service area of the key service unitand approaches another portable telephone key service unit. Therefore,the portable telephone set becomes in capable of communicating with thekey service unit with which it has already got in contact. In concreteterms, if the car goes at 36 Km per hour, it runs 10 m per second.Provided portable telephone key service units are installed at intervalsof 25 m, the portable telephone set in the car has to acquire the downcontrol channel of a new key service unit every 2.5 second.

In such a case, even if a communication channel can be establishedbetween a certain key service unit and the portable telephone set, thechannel must be switched every 2.5 second. This is undesirable becauseineffective operations of the system increase and various noises alsoincrease which impair the speech quality of the communication channel.To avoid this, in the portable telephone set of the present inventionthe noise level detector shown in FIG. 5A notifies the controller of theoccurrence of fluctuation of a radio wave field strength (a noise levelfluctuation) excessive of a fixed value. Then the controller controlsthe oscillation frequency of the receiving frequency synthesizer toacquire the down control channel emitted from the wide area portabletelephone set calling fourth class radio master station (KRC-IV) in FIG.5B, instead of acquiring the down control channel from the portabletelephone key service unit. Further, the portable telephone set requeststhe key service unit to demand an exchange KTC-I to call the portabletelephone set in the wide area calling mode (the fourth class). Theexchange KTC-I judges that the portable telephone set is being carriedon a running car and requests a land mobile radio telephone exchange MTC(see FIG. 5B), which administers the same area as the exchange KTC-I, tocall the portable telephone set PID₁ from the fourth class radio masterslation KRC-IV, using its down control channel. In practice, the requestsignal therefor is transmitted via a route[KTC-I→KTC-II→KTC-III→KTC-IV→MTC].

The fourth class radio master station KRC-IV has a transmitting powerlarge enough to cover a service area with a radius of 3 to 5 Km as inthe case of the pocket pager service of the NTT. Accordingly, theportable telephone set can receive the down control channel of thefourth class radio master station without an abrupt fluctuation in theinput electric field.

If an incoming call occurs in this state, the portable telephone setPID₁ is called from the fourth class radio master station KRC-IV, sothat the call bell shown in FIG. 4A can be rang. The portable telephonesubscriber can answer by using a part of the function of the land mobileradio telephone, as described later.

The above description has been made in respect of an ordinary automobilewith a very small capacity. In the case of a bus with a large capacity,if many passengers carry portable telephone sets with them individually,they cannot receive incoming calls in the land mobile radio telephonemode, but they can be called by the operation in the above-describedcalling mode.

Similarly, in the case of a ship, train, or airplane with manypassengers aboard, the portable telephone set is held in the maritimeradio telephone mode and also in this case it can receive an incomingcall, using the down control channel of the wide area portable telephonecalling fourth class radio master station KRC-IV. It is needless to saythat an outgoing call can be made from such a vehicle throughutilization of such an overlap technique as described later.

The above description has been given of the portable telephone system ofthe business district mode, and the portable telephone system of theresidential district mode is free from such a trouble as referred toabove because the portable telephone key service unit does not send outthe downward control channel at all times. That is the portabletelephone set is receiving in the cordless telephone mode and in thewide area calling mode (the fourth class), while switching therebetween,so that if an incoming call occurs in the wide area calling mode, theportable telephone is called.

In a situation where it is difficult to receive radio waves from theportable telephone key service unit in an underground parking lot orlike place, the portable telephone set responds to a signal from thenoise level detector (FIG. 4A) to receive radio waves from a wide areaportable telephone set calling first class radio base station, and henceis capable of receiving an incoming call as is the case with the above.This will also described in detail later.

Next, a description will be given of a PBX or radio channel controlequipment which is provided in the premises of a company or in a largebuilding and is capable of performing the same operation as that of thefirst class exchange.

The portable telephone system of the present invention enables everyportable telephone subscriber to originate an outgoing call to andreceiving and incoming call from any other telephone subscriber and tokeep communication with him while walking around. This mechanism willalso be explained. FIG. 5D shows, by way of example, the arrangement ofthe portable telephone system of the present invention when employed inthe premises of a company. In FIG. 5D, even if the portable telephoneset 1 (PID₁) is carried along paths near portable telephone key serviceunits 1A, 1B and 1C disposed apart in the previses, the portabletelephone set 1 is capable of keeping communication, as described below.

In this instance, radio channel control equipment RC is provided, whichis connected via a transmission line to each portable telephone keyservice unit and is further connected to a PBX (an exchange),corresponding to each channel, as shown. The PBX accommodates anordinary fixed telephone set as well. In addition, the PBX and the firstclass exchange are interconnected via a subscriber line.

Now, assume that the portable telephone set originates an outgoing callto an ordinary telephone set (T₁) placed under control of the firstclass exchange. The operation for the outgoing call will be describedlater. Then assume that the portable telephone set is in contact withthe telephone set (T₁) and is carried away from the vicinity of the keyservice unit 1A toward the key service unit 1B as shown. In this case,when the portable telephone set PID₁ goes away more than 25 m from thekey service unit 1A, the speech quality become deteriorated. This ismonitored by an S/N monitor in the radio channel control equipment RC(see FIG. 5E). When the S/N (the signal-to-noise ratio) drops below afixed value, the S/N monitor requests a communication channel controllerto switch the channel 1A-PID₁ to a channel 1B-PID₁. FIG. 5E illustratesthe constitution of the radio channel control equipment RC. In responseto the request the communication channel controller (CPU) retrieves itsPID, SID memory, confirms the state of communication between theportable telephone set 1 (PID₁) and the key service unit 1A (SID₁),confirms that the key service unit 1B is not in contact with otherportable telephone set, and then switches the key service unit 1A to 1B.This is done by opening a switch SW₃ (A black triangle shown in FIG. 5Emeans the connection between the key service unit (A and the telephoneset T₁.) of a channel switching unit and closing a switch SW₂ (A whitetriangle in FIG. 5E is changed to a black one.) under control of thecommunication channel controller (CPU).

Upon completion of the above operation, the user of the portabletelephone set 1 can keep on communication with the telephone set T₁while walking.

Also in the case where the portable telephone 1 (PID₁) moves away fromthe key service unit 1B and approaches the key service unit 1C, thecommunication can be maintained by switching the channel PID₁ -1B to achannel PID₁ -1C.

In the above the radio channel control equipment RC possesses thechannel switching function. This is a system configuration which issuitable for use in the case where a company or the like is large-scaleand has its premises at various places. But when the premises are at oneplace or reratively narrow, it is economically advantageous toincorporate the radio channel control equipment RC in the PBX.

Since portable telephones used in ordinary residences are notaccommodated in such a PBX or radio channel control equipment RC, theyare accommodated directly in the first class exchange. In this case, thefirst class exchange is equipped with the above-noted function of theradio channel control equipment, therefore, portable telephonesubscribers can continue communication while walking, by virture of thesame channel switching function as described above.

Next, another embodiment of the portable telephone system of the presentinvention will be described in which it has an interface with theexisting national telephone network, for example, the NTT telephonenetwork. FIG. 5F shows this embodiment. As shown in FIG. 5F, theportable telephone network of the present invention and the NTTtelephone network have an interface therebetween at a high-randingswitching stage, but they are entirely separate at second and lowerclass exchanges. This is characteristic of this embodiment and makes thesystem more independent than the system of FIG. 5C which uses exchangesof respective stages at nodes of the NTT telephone network. In thiscase, it is possible, of course, to accommodate ordinary telephone sets,pocket pagers as well as portable telephone sets in the first classexchange KTC-I and the land mobile radio telephone system in theexchange KTC-III or KTC-IV. The system configuration exemplified in FIG.5F is suitable for use in the case where a business entity differentfrom NTT operates the portable telephone network.

While in FIG. 5F three transmission lines are shown for linkage with theNTT national telephone network, they may also be reduced to one or two.

Although in the above-described system configurations FIGS. 5A, 5B, 5Cand 5D the number of classes of exchanges have been described to befive, this does not necessarily mean that the use of such five classesof exchanges is optimum. This is the conclusion reached after takinginto consideration the population, area and shape of our country andeverything, in designing a nationwide portable telephone network atpresent. However, the optimum number of classes of exchanges will changewith the movement of population, changes in the environment of the lifeof the people, or changes in the costs of hardware and software for thissystem.

Also when the system of the present invention is put to use in a foreigncountry, the number of classes will change substantially with itspopulation and national traits.

(7) Constitution of the Portable Telephone System of the PresentInvention at an Early Stage of Introduction

FIG. 5C shows the system configuration of the portable telephone systemof the present invention which is put to use in 23 Wards of Tokyo at anearly stage of introduction.

In this case, a cordless telephone key service unit (fixed radioequipment), which is substantially the same functions as those of theexisting NTT cordless telephone, is provided in each home or office.This cordless telephone key service unit is accessible to and from adesired portable telephone set. Further, a radio transmitter-receiverequipped with substantially the same functions as those of the cordlesstelephone key service unit is mounted on each pole on the streets. Thesedevices are accommodated in an exchange of a telephone station or PBX inan office as is the case with the existing cordless telephone system,and they are handled in the same manner as in the case of an ordinaryfixed telephone system. However, the above-mentioned exchange or PBXwill hereinafter be referred to as a first class exchange. This exchangehas a memory (a subscriber information memory) for storing, changing anderasing the current positional information of each portable telephoneset.

It will be described below that only with these cordless telephone keyservice units, the portable telephone set of the present invention isable to originate an outgoing call and receive an incoming call atalmost all places in the 23 wards of Tokyo on the ground that severalfunctions mentioned above and essential to the portable telephone systemare added.

Recently the Ministry of Posts and Telecommunications of Japan has,published a material in which it is estimated that the number ofcordless telephones demanded in Japan in 2000's will be ten million.This estimation is reasonable in view of the numeric values (1) to (7)in the afore-noted material "Long-Term Prospects for Utilization ofRadio Frequency Spectrum". It is presumed from the above that the numberof cordless telephones which will be demanded in the 23 wards of Tokyowill be one million. Since the total area of the 23 wards is 581 Km²,there will be 1721 cordless telephone sets per square kilometer.##EQU10## Accordingly, one cordless telephone set will be present in asquare with a side of 25 m. ##EQU11## The above calculations were basedon the assumption that traffic would be uniform, and this assumption isconsidered reasonable because the number of sets demanded is extremelylarge.

As a result of the above calculations, one cordless telephone keyservice set will be installed in each square with each side of 25 m ifthe traffic is uniform. On the other hand, since it is considered thatthe cordless telephone key service unit has a service area with a radiusranging from 25 to 50 m, it will be seen that in the 23 wards of Tokyoin 2000's any portable telephone set can originate an outgoing call andreceive an incoming call when it has succeeded in accessing any one ofthe cordless telephone key service units.

However, since there are broad roads and playgrounds, undergroundshopping centers, etc., in the 23 wards of Tokyo, there are places whereradio waves from cordless telephone key service units installed indoorscannot be received. Accordingly, it is necessary that, in suchdistricts, transmitter-receivers having the same functions as those ofthe cordless telephone key service unit be installed on poles, on thestreets, on the walls of buildings, etc. and that thesetransmitter-receivers be accommodated in exchanges of telephone stationsas in the case of the cordless telephone. Besides, a number of high-risehousing developments have been built in recent years; and so that thismust also be taken into consideration from the viewpoint of the radiowave propagation characteristic.

Moreover, when a large number of peoples use their portable telephonesets at a time, there is a fear that they become incapable ofcommunication because of traffic congestion. This will be describedlater.

In addition, in order that outgoing and incoming call operations may beperformed in an automobile or like high-speed vehicle, it is necessaryto link the portable telephone system with the land mobile radiotelephone system and other mobile communication systems. This will alsobe described later.

(8) Study of Traffic of the Portable Telephone for Use in the CordlessTelephone Mode

It is apparent from the above that in the case of using the portabletelephone system of the present invention in the 23 wards of Tokyo, theportable telephone set is capable of communication almost all over the23 wards of Tokyo when it is used in the cordless telephone mode. Sincea large number of subscribers use their portable telephone sets at thesame time, however, it must be considered in terms of traffic whethersatisfactory communications can be achieved. From the technical point ofview, there is no problem in this respect as described below.

In the existing NTT cordless telephone, the same portable telephone sethas 46 channels; namely, the multichannel access technology is employedby which when a certain channel is busy, an idle channel is searched andused.

Next, the number of portable telephone subscribers that can beaccommodated will be calculated on the assumptions that the portabletelephone set of the present invention also utilizes the multichannelaccess technology and that the number of usable channels are the same asin the case of the cordless telephone system.

The following various values are used as conditions for use of theportable telephone.

i) The number of repetitive zones is 25. This is intended to ensure thatchannels in adjacent zones are not used at the same time so as to avoidinterference of radio waves.

ii) Traffic is 0.03 Erlang (the frequency of use per day: 6 times, 3minutes per call, busy hour call rate: 1/10). Traffic for registrationof position and for new services is 0.02 Erlang. The former is threetimes larger than the traffic of the existing land mobile radiotelephone system.

iii) Blocking probability B=0.03 This is the same design condition asthat of the existing land mobile radio telephone system.

iv) It is assumed that the total area of the 23 wards of Tokyo is 581km² and one-million key service units are installed therein. This valuewill be reasonable on the assumption of a system which covers all thetelephone systems (1) to (7) mentioned in the aforementioned material"Long-Term Prospects for Utilization of Radio Frequency Spectrum".

Based on the above preconditions, the traffic which can be processed inthis portable telephone system can be given as follows: ##EQU12## wherea(46, 0.03) is traffic which can be carried as mentioned previously, interms of Erlang. That is, 762 subscribers can use their portabletelephone sets in a 25 square meter area under the above-saidconditions. Since the number of repetitive zones is 25, the number ofsubscribers accommodated per zone is as follows: ##EQU13## That is, 30subscribers can use their portable telephone sets in a 25 square meterarea under the above-said conditions. Accordingly, in a 1 squarekilometer area: ##EQU14## Over the entire area of the 23 wards of Tokyo:

    58800 (subscribers/km.sup.2)×581 (km.sup.2)=28352800 (subscribers/23 wards)

Namely, about twenty-eight million subscribers can access the system.The above calculations were made on the assumption that the trafficdensity inside the 23 wards of Tokyo is constant. In practice, however,many portable telephones will be used in the wholesale market, areas forspecial events, etc. Assuming that the traffic density in such a placeis 4 times higher than an average density, the number of portabletelephone sets which can be accommodated is about 7.1 millions asfollows:

    28352800×1/4=7088210

Since the population inside the 23 wards of Tokyo is about 8.6 millionsat present, it is presumed that the above-said value is greater than thenumber of peoples who require portable telephone sets, indicating asufficient capacity. From the above it is seen that the numbers ofsubscribers who can be accommodated in the portable telephone systems ofthe residential district mode and the business district mode, in thisexample, are as follows:

(1) Residental district mode

8 subscribers per portable telephone key service unit (Eight portabletelephone sets must be accommodated.)

(2) Business district mode

30 subscribers per portable telephone key service units (Thirty portabletelephone set must be accommodated.)

In practice, however, traffic from portable telephone sets increases ina crowded place such as an amusement district, area for special event,or ballpark, it is necessary to install many portable telephone keyservice unit in the same place. Technically this is easy, and in thiscase the key service unit will be arranged so that many radios areprovided in the same frame as in the case of a land mobile radiotelephone base station. In future the amount of traffic will increaseand the portable telephone will be used for business as well; therefore,only 46 channels assigned at present will be insufficient to accommodatean increasing number of portable telephone sets. In practice, a maximumof 200 channels will be needed after 5 to 10 years. However, the presentinvention sufficiently applicable and the present frequency assignment.

Incidentally, the existing land mobile radio telephone system isassigned 600 channels, whereas the number of channels needed in thepresent invention is only 1/3 of the above.

In addition, future progress of the diversity technology will reduce thenumber of repetitive zones (The numbers of zones used at present, 25,can be reduced about by half, 12.) or reduce the spacing of carrierfrequencies per channel (The efficiency of frequency utilization israised by decreasing the present 12.5 KHz spacing to a 10 KHz one orimproved drastically by the introduction of the digital technology.)Accordingly, there is the likelihood of the existing working frequencyband width remaining virtually unchanged.

(9) Embodiment of a System Coexistent with Existing Various MobileCommunication Systems

The portable telephone system of the present invention is a system whichwill, in its ultimate form, enable the same portable radio terminal toperform the originating and incoming call operation at any desiredplaces all over the country. Since it will be many years before thesystem can be used in its entity, it will be introduced step by step. Inthose areas where the system has not been introduced, it is linked withvarious other mobile communication systems. Also in this case, it ispossible to obtain substantially the same results as those obtainablewith the present invention, as described below. This embodiment is toprovide a system which enables the portable telephone to be used in thefollowing modes in the following cases:

i) In office and residence:

Cordless telephone mode

ii) While walking outdoors:

Cordless telephone or pocket pager mode

iii) On automobile:

Land mobile radio telephone mode

iv) On train:

Train telephone mode

v) On ship:

Maritime mobile radio telephone mode

vi) On ship which performs maritime satellite communication:

Maritime satellite communication mode

vii) On airplane: Airplane radio telephone mode

FIG. 5A shows the constitution of the national telephone networkaccording to the present invention Briefly stated, the portabletelephone set (a terminal) for use in the system of the presentinvention is arranged so that in each of the above-said modes it can belinked with the existing terminal. In an office or residence theportable telephone is used in coexistence with the existing cordlesstelephone. (Since the two telephone systems can be used as if theyconstitute a single system, this state will hereinafter be referred toas superposing.)

The portable telephone terminal is designed so that When brought into anautomobile, it can be connected to an interface of a land mobile radiotelephone terminal. The portable telephone system is used in a manner tosuperpose with the land mobile radio telephone system.

The system configuration of the present invention can easily be modifiedfor use in superposing relation with any of the pocket pager, traintelephone, maritime mobile radio telephone, and other systems.Therefore, the portable telephone terminal of the present invention canbe used in the mode of each system.

The following will describe in detail that the system of the presentinvention is possible technically and is reasonable from the economicalpoint of view.

(9-1) Functions to be Added to Cordless Telephone System for Use inCordless Telephone Mode

At present the NTT cordless telephone is used in our country. The systemof this kind is composed of a portable telephone set and a key serviceunit which is connected to the portable telephone set via a radiochannel communication circuit and an exchange via a wire communicationcircuit. The portable telephone set and the key service unit usuallybear a specific relation such that the former is subordinate to thelatter. The telephone set cannot communicate with a key service unitother than the specified one even if they happen to lie at a shortdistance over which radio channel communication could be establishedbetween them. Similarly, the key service unit is not permitted tocommunicate with other telephone sets than the specified one.

However, in order that the portable telephone set of the presentinvention may be used in the cordless telephone mode, the portabletelephone needs to be equipped with means by which it is capable ofconnecting to key service units other than that which is connected tothe portable telephone set through a radio channel communicationcircuit. With the provision of such means, even if the portabletelephone set is carried to any place, communication can be maintainedso long as there is, at that place, a key service unit which satisfiesrequired speech quality. The system configuration in this case is thesame as shown in FIG. 3A, to which is added functions described below.The portable telephone set is depicted in FIG. 4A.

In order to permit the use of the portable telephone set of the presentinvention in the cordless telephone mode, the existing cordlesstelephone key service unit must be equipped with the followingfunctions.

i) The cordless telephone key service unit accepts and stores theposition register signal from any portable telephone set and transmitsits subscriber information to a first class exchange such as radiochannel control equipment, PBX, or exchange of a central office.

ii) When receiving an incoming call to the portable telephone set, thecordless telephone key service unit sends out its PID signal, using acontrol channel.

iii) In the case of communication between the portable telephone set ina roam area and the portable telephone key service unit, the cordlesstelephone key service unit the PID information of the calling portabletelephone set and the duration of the communication to the subscriberinformation memory (a charging section) of the first class exchange.

(9-2) Functions to be added to Radio Channel Control Equipment forCordless Telephone, PBX (see FIG. 5D), or End Office Exchange (Theexchange equipped with the additional functions will hereinafter bereferred to as a first class exchange.)

(i) The first class exchange stores PID signals and other subscriberinformation of portable telephone sets sent from the cordless telephonekey service unit.

(ii) When having accepted the PID signal of only that one of theportable telephone sets which is in a roam area, the first classexchange checks its contents. Having found that the portable telephoneset is being used in an n-th class roam area, the first class exchangenotifies the subscriber information memory of an n-th class exchange ofthe current position of the portable telephone set. In practice, thefirst class exchange needs only to transmit the signal to the subscriberinformation memory of the second class exchange. The reason for this isthat the second class exchange also checks the contents of the PIDsignal and judges whether to send it to a higher-ranking exchange.

(iii) When the first class exchange receives an incoming signal to theportable telephone set from a portable telephone subordinate to thesecond class exchange or the first class exchange or an ordinarytelephone set, the first class exchange sends out the incoming call tothe key service unit concerned.

(iv) The first class exchange is equipped with the above-mentionedfunctions in order to operate the cordless telephone set in the portabletelephone systems of the residential district mode and the businessdistrict mode or as a portable telephone set of the continuous positionregistration request mode.

With such additional functions as mentioned above, the cordlesstelephone can be used as the portable telephone system of the presentinvention.

FIG. 5B shows the internal arrangements of the key service unit and theportable telephone set and the channel structure therebetween. FIG. 7Ashows flows of originating and incoming call operations between the bothdevices.

The above has described that the addition of functions to the existingcordless telephone could obtain the function of the terminal equipmentin the cordless telephone mode of the portable telephone system of thepresent invention. In practice, when the portable telephone system ofthe present invention will have come into wide use, the demand for thecordless telephone will decrease substantially and the portabletelephone system will be used in the field which has been considered asthe field of application of the cordless telephone. However, theafore-noted literature "Long-Term Prospects for Utilization of RadioFrequency Spectrum" does not forecast the appearance of a system whichincludes the existing systems (1) to (7), such as the system of thepresent invention, but the literature estimates that, for example, thenumber of cordless telephone sets will be as large as seven millions allover the country. Therefore, on the assumption of how portable telephonekey service units would be distributed in the service area of eachcordless telephone set when seven million cordless telephone sets havealready been spread throughout Japan, the manner how to use the portabletelephone set of the present invention while walking, in a house and ata crowded place has been described previously, while at the same timepointing out differences in hardware and software between the cordlesstelephone and the portable telephone of the present invention.

When the portable telephone system of the present invention will havecome into full use, the cordless telephone will be dealt with byomitting some of its functions.

(9-3) Functions to be added to the land mobile radio telephone system soas to permit the use of the portable telephone set in the land mobileradio telephone mode

For using the portable telephone set of the present invention in anautomobile, it is a precondition that the existing car telephone beinstalled in the car. The reason for this is that apart from far-offfuture, at the present technological level, the portable telephone setbrought in the car cannot always be used without the aid of the landmobile radio telephone system.

A description will be given first of the configuration of the existingNTT land mobile radio telephone system and the configuration of thenetwork of the present invention.

FIG. 9 illustrates the land mobile radio telephone system at theright-hand side and the network of the present invention at theleft-hand side, the broken line at the center indicating an interface.

For the land mobile radio telephone system shown in FIG. 9 is referredto a literature ("N. Yoshikawa et al, Radio Control System on UHF LandMobile Radio Telephone", Electrical Communication Laboratories TechnicalJournal (NTT), Vol. 26. No. 7, P1871˜1977.)

(9-4) Method of Superposing the Portable Telephone System and LandMobile Radio Telephone System

Now, a description will be made, with reference to FIG. 9, of a methodfor superposing the portable telephone system of the present inventionon the land mobile radio telephone system.

In FIG. 9 the portable telephone network of the present invention shownon the left-hand side of the broken line is linked with the land mobileradio telephone network from an exchange KTC-IV to land mobile radiotelephone exchange MTC. That is, the fourth class exchange is connectedto the land mobile radio telephone exchanges (MTC). The land mobileradio telephone exchanges are interconnected via a straight line andeach exchange is connected to radio communication circuit controlstations and base stations via communication circuits and controlcommunication circuits. Each base station and each car telephones areinconnected by radio. The functions of each station forming the landmobile radio telephone system will be described later.

There are several superposing methods.

A method which is the simplest and does not impose any burden on theland mobile radio telephone system is to bring the portable telephoneset in the car and dial, from its car telephone to the land mobile radiotelephone exchange (MTC in FIG. 9), a special number (for example,##01-XXX-XX-XXX-XXXX, where numerals other than ##01 are the PIDinformation of the portable telephone set and X is an arbitrary one ofnumerals 0 to 9. In practice, since abbreviated dialing is possible,this position registration is easy.), registering the position of theportable telephone set in the subscriber information memory of theexchange MTC. In this case, the exchange MTC must be additionallyequipped with a function of accepting the registration of the positionof the portable telephone set.

The subscriber information memory of the exchange MTC, which has thusaccepted the position registration from the car telephone (whose numberis YY-YYYYY, where Y is an arbitrary one of numerals 0 to 9.), acceptsand stores the current position registration of the car telephone (whichregistration is unnecessary if already registered) as well as theposition registration of the portable telephone set. The exchange MTCsends a signal to a fourth class exchange which controls the exchangeMTC, notifying it of the fact that the portable telephone set is in thestate of being superposed on the land mobile radio telephone system andits position has already been registered in the subscriber informationmemory of the exchange MTC. Then the fourth class exchange decodes thePID information of the portable telephone set and transmits subscriberinformation of the portable telephone set, such as the registeredcurrent position information, to third to first class exchanges whichadminister the portable telephone set. The third to first class exchangestore the transmitted information.

Thus, processing on the side of the fixed station is completed, and itwaits for an outgoing call from the portable telephone set. In thismethod, however, the portable telephone does not originate the outgoingcall but instead the car telephone performs all operations therefor.

Incidentally, the reception of an incoming call can be made easy byholding the portable telephone set in the ON state.

Since the telephone rate must be charged to the account of the portabletelephone subscriber, not the car telephone subscriber, the followingdial operation is performed.

Upon off hooking the car telephone, the following operations i) to iv)for an outgoing call from a mobile station take place: Outgoing callfrom mobile station

i) Upon lifting the handset for originating an outgoing call from themobile station, a call request signal (the calling subscriber's numberand a call indication) is transmitted [(1)]. A radio base stationreceives and sends it to a radio channel control station [(2)]. (SeeFIG. 10A.)

ii) The radio channel control station indicates an idle communicationchannel of the radio service zone concerned, using a transmissioncontrol channel.

iii) The radio channel control station sends out the calling subscribernumber signal to the land mobile radio telephone exchange via a controlchannel.

iv) Then the land mobile radio telephone exchange reads out of itsmemory subscriber data of the calling subscriber and analyzes the data[(3), (4)].

Next, the calling party dials ##02 and then the called party's number.This initiates the following operation (v).

(v) If it is found, as a result of the analysis, that the calling partyis capable of calling [(4)], the land mobile radio telephone exchangemakes the radio channel control station request the mobile station tosend out dial numerals [(5)]. The land mobile radio telephone exchangedecodes ##02 and judges that it is an outgoing call from the portabletelephone set, and then makes its positional information memory retrievewhether the position of the portable telephone set has been registered.When it is found that the portable telephone is superposed on the cartelephone (whose number is YY-YYYYY), the land mobile radio telephoneexchange makes a charging information memory ready for the start ofcharging upon commencement of communication. Further, the land mobileradio telephone exchange notifies a exchange KTC-IV of the outgoing callfrom the portable telephone set [(6), (7)].

vi) After receiving the dial signal, the called party is called viaexchanges KTC-IV, KTC-III, KTC-II and KTC-I in the same manner as in thecase of ordinary telephone. In this case, the number of calls is countedfor the portable telephone set and the telephone set chargeable thereonis charged, for example, once a month. The charging information on theportable telephone set is transferred to a charging section of the firstclass exchange which administers the home area of the portable telephoneset. In the charging section the transferred telephone rate and thetelephone rate in other roam areas are added up and charged to theportable telephone subscriber [(8)].

The above operations are such as shown in FIG. 10. Incoming call to theportable telephone set.

Next, an incoming call will be described.

In this case, it is a precondition that the portable telephone set hasalready registered its position in the subscriber information memory ofthe land mobile radio telephone exchange (MTC).

Assume that the portable telephone set is called from an ordinarytelephone set at a given place and that the calling telephone set is ina place where the portable telephone set (including the fourth classexchange) is not accommodated (administered). In this instance, from thePID of the portable telephone set dialed by the ordinary telephone set,first to third class exchanges which administer the ordinary telephoneset learns that the portable telephone set is subordinate to a fourthclass exchange, and they transfer the PID of the called portabletelephone set to a fourth class exchange which administers them. Thenthe fourth class exchange transfers these signals through a fifth classexchange, or a straight circuit, if any, to the fourth class exchangewhich administers the called portable telephone set. Then the fourthclass exchange makes its subscriber information memory retrieve the PIDinformation. As a result of this, the fifth class exchange finds thatthe portable telephone set is superposed on the car telephone (whosenumber is YY-YYYYY), and instructs the land mobile radio telephone toproceed to a calling operation. This operation is similar to theabove-described car telephone calling operation. In this case, however,the called party's number is the car telephone number (YY-YYYYY), notthe protable telephone set PID. Then, the following operations i) to ix)are carried out one after another.

i) The land mobile radio telephone exchange reads out the calledsubscriber's information from a home memory station to which the calledsubscriber belongs.

ii) If the called subscriber is found idle, the land mobile radiotelephone exchange transmits a call signal via the control channel toeach of the radio channel control stations in the area specified forcalling.

iii) The radio channel control station calls the called portabletelephone through each of its subcordinate radio base stations, using aterminating control channel.

iv) The called mobile station automatically transmits an answer signalthrough the terminating control channel. The radio base station sendsthe received answer signal to the radio channel control station, whichin turn the answer signal to the land mobile radio telephone exchangethrough the control channel.

v) The land mobile radio telephone exchange sends out an audible ringingsignal to the called party and a ring-back tone to the calling party.

vi) After the car telephone subscriber has answered, the exchangeperforms substantially the same operations as those in the case of anordinary telephone. In an event that the car telephone has alreadyreceived a preceding incoming call (or originated an outgoing call) andcannot received the current incoming call, it is possible that the landmobile radio telephone exchange recognizes it and directly calls theportable telephone set PID₁, using radio waves of a wide area portabletelephone set calling 4th class radio base station.

While in the above the calling telephone set and the called portabletelephone sets are accommodated in different fourth class exchanges,communication is enabled also in the case where the calling and calledparties are accommodated in the same fourth class exchange. In thisinstance, the call request signal from the calling telephone set istransmitted to any one of the first to fourth class exchanges by whichthe portable telephone set is administered. The exchange searches itssubscriber information memory and finds that the portable telephone setis superposed on the land mobile radio telephone system through theexchange MTC. Then the fourth class exchange sends the call requestsignal to the exchange MTC. The subsequent incoming call operations areexactly the same as described above.

As is the case with the ordinary telephone, the charging of thetelephone rate to the calling telephone set is carried out in a charginginformation memory of the subscriber information memory of the exchangewhich accommodates the telephone set.

The clearing operation is exactly identical with that in the land mobileradio telephone system described previously.

The portable telephone set can be released from the state of beingsuperposed on the land mobile radio telephone system, by dialing aspecial number (**11-XXX-XX-XXX-XXXX, for example) from the cartelephone to the exchange MTC, removing the registered positionalinformation of the portable telephone set from the subscriberinformation memory of the exchange MTC.

Next, a description will be given of a method which permits the use ofthe portable telephone set in a car, although this method requires somemodification of the land mobile radio telephone system.

In this case, the car telephone set and the portable telephone set arehybrid-coupled and connected in parallel as viewed from the cartelephone station (FIG. 12B). Accordingly, the land mobile radiotelephone must be modified so that the car telephone station has aninterface for signal transmission to and reception from the cartelephone set and an interface for signal transmission to and receptionfrom the portable telephone set.

In concrete terms, the above interfaces can be implemented by thefollowing method (1) or (2).

(1) The car telephone station is equipped with a signal converter, amemory, and a discriminator for an outgoing call from or incoming callto the portable telephone set.

(2) The outgoing and incoming call signal interface of the portabletelephone set is attached to the car telephone set.

As a matter of fact, the method (2) is not advantageous, taking intoconsideration the fact that the portable telephone set is superposed onthe maritime mobile radio telephone system and the airplane radiotelephone system. The reason for this is that it is desirable from theviewpoint of portability that the portable telephone set be as light andsmall as possible. Accordingly, there is no choice but to adopt themethod (2). However, since the land mobile radio telephone system hasalready come into wide use, it is not economical to provide all of theexisting car telephone station with such parts as mentioned above;therefore, the use of the method (2) will be limited. It is practical toemploy an portable telephone adapter. The modification may also beeffected taking the advantage of the occasion of changing hardware ofeach car telephone. FIG. 4A shows an example of the actual connection ofthe portable telephone set. The switches SW₁ and SW₂ are operativelyassociated with each other and are each normally connected to thecontact (1). Where the portable telephone set is superposed on anothersystem, the switches SW₁ and SW₂ are each connected to the contact (2).As a result of this, the transmitting and receiving radio sections ofthe portable telephone set are disconnected from its telephone section(The power supply is also turned OFF.) and perform the same function asdoes the telephone section of the car telephone.

The provision of the above-mentioned interfaces by the method (1) mayalso be taken into consideration in the development of an advance systemof the land mobile radio telephone system. Furthermore, the method (2)is also applicable if the interface between the radio and telephonesections is adapted for use in common to the portable telephone set andthe car telephone set in the modification of the land mobile telephonesystem.

Where the car telephone set is equipped with the aforesaid interfaces bythe method (1) or (2), it is possible to originate an outgoing call fromand receive an incoming call to the portable telephone set brought in acar, as described below.

A description will be given of a method of registering the position ofthe portable telephone set in the exchange MTC in FIG. 9.

Assume that the portable telephone set is in the 0N state, and hence iscapable of originating an outgoing call. In this case, afore-mentionedoperations i) to v) for calling from a mobile station are carried out.The user dials a special number, for example, **01 alone as describedpreviously. The car telephone set automatically transmits a signal[YY-YYYYY+PID] to the radio base station. Upon receiving this signal,the exchange MTC accepts and stores in its subscriber information memorythe current position registration of the portable telephone set as wellthe current position registration of the car telephone set (The positionregistration of the car telephone is not needed if already registered).

As referred to previously, the exchange MTC sends, to the fourth classexchange having an interface with the exchange MTC, a signal indicatingthat the portable telephone set is in the state of being superposed onthe land mobile radio telephone system and has registered its positionin the positional information memory of the exchange. Then the fourthexchange decodes the PID information of the portable telephone set andtransmits its subscriber information to the third to first classexchanges which administer the portable telephone set.

The outgoing call from the portable telephone set after registration ofits position can be achieved by exactly the same operation as that foran outgoing call from the car telephone set. The charging of thetelephone rate to the portable telephone is also performed by the samemethod as described previously.

An incoming call is also processed in the same manner as describedpreviously, but ringing is provided to the portable telephone set, notto the car telephone set, and the user can communicate with the callingparty, using the portable telephone set brought in the car.

In this case, the portable telephone set can be dissociated from theland mobile radio telephone system simply by dialing a special number(**11, for example) from the portable telephone set.

Next, a description will be given of a method for superposing theportable telephone set on the land mobile radio telephone system. Thismethod calls for a heavier burden on the land mobile radio telephonesystem and appreciable modifications thereof but does not involve anychanges in handling software and hardware of the portable telephone set.

According to this method, the car telephone station installed in the caris operated as if it were a portable telephone key service unit. The cartelephone must be modified as follows:

(1) To equip the car telephone station with the function of the portabletelephone key service unit.

(2) To strengthen the function of a car telephone station controller formaking the function (1) and that of the car telephone compatible.

It is not advisable to modify all car telephone stations; therefore, itis practical to modify only the car telephone station on which theportable telephone set is desired to be superposed, or employ adaptersfor the functions (1) and (2).

By applying the same method as described above, the portable telephoneset of the present invention can be superposed on the maritime mobileradio telephone system and the airplane radio telephone system as well.FIGS. 5B or 5C shows the connection of these systems and the networkstructure of the present invention. The both systems have an interfacewith the exchange KTC-IV.

(9-5) Method of Superposing Portable Telephone System and Pocket PagerSystem

As already described, it is possible for the portable telephonesubscriber to originate an outgoing call from and receive an incomingcall to the portable telephone set in the cordless telephone mode whilewalking on a street. Now, a method of superposing the portable telephoneset on the existing pocket pager system will be described below.

The superposition of the portable telephone system on the pocket pagersystem has the following significance.

In a city area the portable telephone set can be used in the cordlesstelephone mode, but the transmitting power of the portable telephone setof the present invention and the cordless telephone set is as weak as 6mW or so. Accordingly, where a source of jamming exists in the spacenear the portable or cordless telephone set, the radio wave propagationcharacteristic is deteriorated, resulting in speech quality beingdegraded or communication becoming impossible in some cases. It must betaken into account that this often occurs in large building, undergroundshopping centers, underground parking lots and similar places.

On the other hand, the transmitting power of radio frequency spectrumemitted from the base station of the pocket pager system is as large as250 W or so and the existing system maintains an appreciably excellentcalling rate even in a closed space of the first basement. Accordingly,assume that where the portable telephone set in its stand-by state (inthe state of acquiring the down control channel) in the businessdistrict mode at one place becomes incapable of acquiring the controlchannel of the cordless or portable telephone key service unit becausethe portable telephone subscriber has moved from there to another placethe radio frequency of the control channel of the key service unitacquired by the portable telephone set is changed to a pocket pagercalling frequency. This is possible in terms of hardware. In the case ofthe portable telephone set shown in FIG. 4A, when the noise level of thenoise level detector exceeds a fixed value, the frequency of thereceiving frequency synthesizer is switched to the calling frequency ofthe pocket pager system under control of the controller. Thereafter, theportable telephone set performs exactly the same operations as does thepocket pager of the pocket pager system. FIG. 7B shows a flow of theincoming call receiving operation. Suppose that a call base station ofthe pocket pager system is additionally equipped with a function ofsending out a calling wave when it receives from the exchange KTC-I (inFIG. 5C) a control signal for calling PID information of the pocketpager.

When the pocket pager is called from the base station in such a state, acall switch is turned ON (with the handset hung off). At this time, ifthe display of the portable telephone set indicates that an outgoingcall is possible, it means that the portable telephone set is acquiringthe down control channel of the nearest cordless (or portable) telephonekey service unit (SID). Then the portable telephone set sends out anoutgoing call signal together with its PID information, using the upcontrol channel. The exchange KTC-I receives the PID+SID signal, findsthat the portable telephone set PID is in the service area of the keyservice unit SID, and then sends out the incoming call signal to the keyservice unit SID.

The key service unit SID accepts the incoming call signal from theexchange KTC-I and sends out it to the portable telephone set afterconfirming its PID₁ information. The subsequent operations are the sameas in the case of the incoming call in the cordless telephone mode (seeFIG. 7A). In this while, a local exchange (the first class exchange inthe present invention) for the pocket pager offers a verbal service, forexample, "We are calling by pocket pager. Please hold the line." (seeFIG. 7B)

If the display of the portable telephone set indicates that an outgoingcall is impossible, the subscriber has to move, for instance, from thebasement to the first floor or from an underground shopping center to astairway leading to the ground. Then when the display indicates that anoutgoing call is possible, it means that the portable telephone has justacquired the down control channel of the nearest cordless (or portable)telephone key service unit, enabling communication with the callingparty as in the above case, FIG. 7B shows the above-described operationsfor each part of the network structure of the present invention.

Next, a description will be made of the function of a wide area portabletelephone calling fifth class base station (a satellite KTC-V).

It is expected that in the year of 2000 or so the portable telephonesystem of the present invention will have been so widespread that anyone will be able to make phone calls to the far corners of the countryat any time. In 2000's, however, there will still remain areas theportable telephone set of the present invention cannot fully beutilized. For example, in steep mountains like the Japan Alps, theportable telephone set cannot obtain a sufficient input power with radiowaves from the nearest portable telephone key service unit or pocketpager base station, and hence cannot receive any incoming call signals.The same is true of a portable telephone subscriber on a ship out at seaor an airplane.

In such a case, it is possible to use a private communication method orsome other public communication system as well, but the portabletelephone system of the present invention is also applicable, utilizingthe wide area portable telephone calling fifth class radio base stationwhich uses a satellite. In the following cases this radio base stationperforms calling after receiving a control signal from the fifth classexchange.

(1) In the case where the subscriber predetermines the period ofreceiving incoming calls and the area of utilization and the radio basestation calls the subscriber in response to specified ones of incomingcalls (or all incoming calls).

(2) In the case where no answer is given to an ordinary incoming call,where the portable telephone set is superposed on an wide area callingn-th class radio base station (where n=1, 2, 3 and 4) or on the landmobile radio telephone system, where no answer is given to calling fromthe wide area fourth class radio base station, or where calling is madeon a contact with the subscriber.

(3) In the case where the called subscriber is an important person (aVIP) or where an emergency communication is needed.

If the ship is provided with equipment for other communication system,functions similar to those in the case of superposing the portabletelephone system on the land mobile radio telephone system are added tothe communication equipment of the ship, enabling it to perform outgoingand incoming operations. That is, calling for an incoming call isperformed by the satellite and communication by the portable telephoneset after receiving the call is called out using the communicationequipment of the ship. This applies as well to the portable telephoneset on an airplane.

In steep mountains like the Japan Alps, even if wide area calling isperformed by the satellite, the portable telephone set cannot answerunless radio equipment is provided in its vicinity, so that it isdesirable that communication information be contained in the callsignal. In this instance, the called subscriber becomes capable ofreception by displaying the transmitted communication information on thedisplay of his portable telephone set or hearing it as verbalinformation.

Now, a description will be given of the traffic of the transmittedsignal from the wide area calling n-th class (where n=1, 2, 3, 4 and 5)radio base station. Almost all the traffic in the portable telephonesystem of the present invention is the traffic in the cordless telephonemode. Accordingly, the wide area calling is not so often effected as awhole, but the traffic of the first class radio base station isrelatively large; and in decreasing order of traffic are the second,third, fourth, and fifth class radio base stations. That is, the fifthclass radio base station, i.e. the satellite has the smallest traffic.Since the satellite is used widely for other communications, it isconsidered that the system of the present invention will share thesatellite with other communication systems. Therefore, the running costsof the system will not become extremely high and the system of thepresent invention will be used harmoniously as a whole.

(9) Other Functions of the Portable Telephone Set

Since the portable telephone set of the present invention is capable ofperforming outgoing and incoming call operations all over the country,it has various functions other than the communication one, as mentionedbelow.

The most striking function is a credit function which results frommarked improvement of the identification capability of the portabletelephone set as compared with the existing magnetic card or IC card.Table 4 shows the comparison of their functions for identification use.

                                      TABLE 4                                     __________________________________________________________________________    Comparison of functions of IC card and portable telephone set as ID                    IC (magnetic card)  Portable telephone set                           __________________________________________________________________________    Size, shape                                                                            A little larger than a name card, easy                                                            Larger and heavier than IC card because of       standarization                                                                         to carry, and negligibly lightweight.                                                             the inclusion of the communication                                            functions,                                       etc.     Standardized and reader also standard-                                                            but not inconvenient to carry.                            ized (magnetic card).                                                                             Concretely, a size of 100 to 200 cm.sup.3                                     and a                                                     Not so standardized as in the case of                                                             weight of 100 to 200 grams will be realized               magnetic card, but there are signs of                                                             in 2000's. For standardization, respective                standardization (IC card).                                                                        parts of different function, for example,                                     radio section, handset, display, memory,                                      etc.                                                                          must be standardized individually.               Storage Capacity                                                                       Magnetic card: 128 bytes                                                                          Equal to or several hundred times larger                                      than                                             for ID   (128 letters)       IC card through different with size                       IC card: several hundred times                                                larger than magnetic card                                            Communication                                                                          No                  Yes                                              function                                                                      Reliability of                                                                         Magnetic card: Inevitably limited to                                                              Because of large storage capacity like IC        ID function                                                                            a simple checking function such as a                                                              card, complex checking method can be                                          adopted                                                   code number for identifying the owner                                                             for identification of the owner.                          IC card: Far larger storage capacity                                                              In addition, change of stored contents such               than that of magnetic card provides                                                               as code number can be easily done by the                  complex checking functions and                                                                    owner, accessing the center through use of                improves reliability. But limited                                                                 the communciation function.                               specifically to predetermined                                                                     As identification methods of various                      checking functions and incapable of                                                               purposes, such as membership card of golf                 checking as the occasion demands.                                                                 club, certificate of registration of                                          owner's                                                                       official seal, ID certificate for identifi-                                   cation of the owner for voting, ID certifi-                                   cate of identification of the owner for                                       credit, etc., voiceprint is collated with                                     registered one, signature is compared with                                    registered one by referring to the center,                                    and answers are given to inquires for ID                                      check from the center.                                                        By using these communication fuctions,                                        various checking methods can be set.                                          Reliability as ID function is improved                                        drastically.                                     Measures against                                                                       Necessary to inform the center for                                                                Possible to inform the center for                                             invalidat-                                       loss and theft                                                                         invalidating the magnetic card                                                                    ing portable telephone, but also possible                                     to                                                        (IC card)           suspend functions of portable telephone by                                    transmitting special signal from the             __________________________________________________________________________                                 owner                                        

(i) Credit card function

The portable telephone sets of the present invention each have PIDinformation different from the others, and hence can be used as a creditcard. This will be described below in concrete terms.

Now let it be assumed that Mr. A, owner of the portable telephone set(PID₁), does his shopping at a store B and the amount payable for hisshopping is 85,000. When Mr. A turns ON the power source of the portabletelephone set near the check-out counter in the store B, it acquires thedown control channel of a portable telephone key service unit (SID_(x))installed in the store and set in the portable telephone system of thebusiness district mode, and the position of the portable telephone setis registered as described previously. That is, its position is storedin the subscriber information memory of the first class exchange of theroam area.

Next, Mr. A presses a function button and numeral buttons of theportable telephone set to display "###85000" on the of the portabletelephone display thereof. After having the displayed amount of moneyconfirmed by a cashier of the store, A enters his code number andpresses a call button of the portable telephone set. Then a signal istransmitted via the portable telephone key service unit AID_(x) to thesubscriber information memory of the first class exchange and is storedin the form of PID₁ +SID_(x) +85000 in a credit memory of the specialinformation memory. In this case, however, if Mr. A has a record to hisdiscredit such as insolvency, there will be an answer back refusingcredit to him. After completion of this processing, the exchange KTC-Ianswers back to the portable telephone set PID₁ (or a fixed telephoneset of the key service unit SID₁) by a voice signal "The amount of moneyon credit to the owner of the portable telephone set PID₁ has now beenentered in the memory from the telephone set. The amount of money storedin 85,000." The signal to the fixed telephone set may also be providedby displaying the amount of money 85,000 and the PID₁ information of theportable telephone set PID₁.

Thus, processing for the payment on credit to Mr. A at the store B iscompleted. Then a signal (the amount of money) stored in the creditmemory of the special information memory of the exchange KTC-I istransferred to a credit sales company C under contract to the store B onevery fixed day (or every day). The company C totals the transferredamounts of money, charges the bill to Mr. A's appointed bank accountmonthly, and transfers the predetermined amount of money to the accountof the store B. Thus, payment of money for Mr. A's purchase price oncredit at the store B is completed.

(ii) Portable telephone set usable with a telephone card

The PID information of the portable telephone set of the presentinvention is appended with a code number so as to prevent the portabletelephone set from being abused even if it is stolen. In view of recentrapid distribution of telephone cards, it will greatly serve theconvenience of telephone card owners if the portable telephone set canbe used with the telephone card.

There are two methods of practical use as follows:

(1) The portable telephone set is designed to receive a telephone cardcan be inserted thereinto and operate in the same manner as does anordinary card type public telephone set now in use.

(2) A telephone card adapter is attached to the portable telephone setso that it can be used in the same manner as in the case (1).

It is considered it possible to employ the both methods in the futuresince a telephone card reader will have been miniaturized; but, it ispreferable to apply the method (2) at the present stage ofpopularization of the portable telephone and introduce the method (1) inthe more advanced stage.

It is also possible to adapt the portable telephone set for use withmagnetic and IC cards, filling diversified needs of users.

(iii) Message service

A message to the portable telephone subscriber is stored in thesubscriber information memory of a first class exchange whichadministers the area of the portable telephone set PID. When thesubscriber presses a message receiving function button of the portabletelephone set, the message stored in the first class exchange istransmitted to the subscriber.

(iv) Guide function

Where the portable telephone set is held ON in the cordless telephonemode, it always acquires the down control channel of the portabletelephone key service unit (of the portable telephone system in thecordless telephone mode and in the business district mode) installed ina residence, park, or like place. This enables the portable telephonesubscriber to know the name of the place where he is, by displaying theSID information of the key service unit on the display of his portabletelephone set. That is, the SID information of the key service unit withwhich the portable telephone set is in contact through the down controlchannel is available on the portable telephone set simply by depressingits function button for transmitting an SID information request signalto the key service unit. Moreover, since the SID information of the keyservice unit contains the address of the place where it is located, itis even more convenient to the portable telephone subscriber if henotifies the first class exchange of the key serive unit at thedestination of his visit in advance (a guide service mode). In thiscase, when the portable telephone subscriber approaches the destinationof his visit, the first class exchange rings the bell of the portabletelephone set, and when the portable telephone set acquires the downcontrol channel of the key service unit at the destination of the visit,a ringing tone of a higher level is produced, indicating the currentposition of the subscriber. In this way, the subscriber can easilyarrive at his destination.

(v) (Function as a substitute for an identification card)

(1) Substitute for driver's license

The portable telephone set can be used as a driver's license by addingits information (MPID) to the PID information of the portable telephoneset. The MPID information includes the kind of licence, the driver'srecord, age and so forth. In this case, the MPID information stored inthe subscriber information memory of the portable telephone set needs tobe transferred to an organization administered by the Public SafetyCommission.

(2) Substitute for membership card of a golf club or some otherorganization

The portable telephone set can be used as a substitute for a membershipcard of a golf club by adding its information (GPID) to the PIDinformation of the portable telephone set.

The portable telephone set can also be used as an attendance card in acompany, office, or the like. Further, the portable telephone subscriberis capable of opening or closing his electronic locker by radio.

Besides, the portable telephone set can be used as a passport(PID+passport PID (PPID)) in future under un agreement made with foreigncountries. This will greatly improve the efficiency of the issue ofpassports.

(3) Substitute for a railway ticket, admission ticket of a theater, orthe like

By inserting the portable telephone set into a device for confirming itsID information at a wicket of each of railway stations where theportable telephone subscriber gets on and off a train, the railway farecan be paid in the same manner as in the case of shopping on credit asdescribed previously.

(4) Means for the realization of a paperless society

The portable telephone set can be used as a ballot in a general or localelection. If the portable telephone subscriber obtains permission fromthe election administration committee by notifying it that his PIDinformation is in agreement with the contents of his resident's card,the subscriber can vote, for example, at home, without taking thetrouble to go to a polling station. In this case, when the subscriberdials a vote number, for example, ###11 after confirming the name andnumber of a candidate displayed on his portable telephone set, thesignal is transmitted via the subscriber information memory of theexchange KTC-I to an elector information memory administered by theelection administration committee of the district concerned. In thismemory the PID information of the portable telephone set and the votedcandidate are confirmed and, if the vote is found valid, it istransferred to a vote collecting center. Of course, qualified voters whohave no portable telephone sets can vote in the conventional manner, andeven if the portable telephone subscriber can also vote in theconventional manner when he wishes so. The polling station and theelector information memory are interconnected by a straight line so thatit is immediately found out whether the portable telephone subscriberhas voted or not, on the basis of his PID information. For votingthrough the portable telephone set, the subscriber's voiceprint;password (election PID), or signature must be notified in advance inorder to prove the subscriber's identity when voting. Similarly, thisfunction of the portable telephone set can be utilized for theinhabitant's voting, a national census, and so forth.

(vi) Function as an input terminal for depositing in and withdrawal froma bank and for buying and selling securities such as bonds and stocks

The portable telephone set can be used as a substitute for theabove-said input terminal by utilizing the PID information and codenumber of the telephone set or the subscriber's voiceprint or the like.

(10) Use and System Operation of Portable Telephone Set

Next, a description will be given of the actual use of the portabletelephone set of the present invention as communication means indoors,outdoors, or in car and as a credit card, identification card, or thelike, together with the system operation therefor. Let it be assumedthat in the case of the cordless telephone mode, the portable telephonekey service unit is, in principle, in the business district mode inwhich it transmits its control signal at all times. When the portabletelephone set is in its home area in the portable telephone system ofthe residential district mode, it operates in exactly the same manner asdoes an ordinary telephone set of the existing NTT cordless telephoneand processing in the telephone network is the same; therefore, nodescription will be made in this respect.

i) Outgoing and incoming calls in first class roam area

Now, consider that Mr. A, a portable telephone subscriber whose PIDinformation will hereinafter be referred to as PID₁, goes for a walk toa park apart from his home area. Mr. A will usually retain the portabletelephone set in the OFF state for power saving purpose. Of course, theportable telephone set may be held in the ON state. In the case of thebusiness district mode, the portable telephone set in the control signalreceiving state receives signals of the down control channels fromportable telephone key service units installed in the neighboringresidences one after another as Mr. A walks down the street, and theposition registration of the portable telephone set is changed for eachkey service unit. That is, an SID signal which is the ID information ofeach key service unit always flows in its down control channel, and whenreceiving the SID signal, the portable telephone set collates it withthe SID signal stored in its memory to find that the former is differentfrom the later (i.e. that the portable telephone set is in the firstclass roam area), and then sends out its PID₁ signal for theregistration of its position to the new key service unit through the upcontrol channel thereof.

The new key service unit SID₂ having received the PID₁ signal searchesits memory to find that Mr. A's portable telephone set is different fromthat which is subordinate to the key service unit. Then the key serviceunit stores the PID₁ information of Mr. A's portable telephone set andrequest the first class exchange to register, in its subscriberinformation memory, the position of the portable telephone set.

The signal which is transmitted from the key service unit to the firstclass exchange in this case is composed of the SID₂ information of thekey service unit and PID₁ information of Mr. A's portable telephone set.Accordingly, the first class exchange rewrites the position of theportable telephone set registered until then in its subscriberinformation memory and stores that the portable telephone set is now inthe service area of the key service unit SID₂. At this stage Mr. A cancommunicate with a third party through the key service unit SID₂. Thatis, Mr. A's portable telephone set is accessible to the key service unitSID₂ for an outgoing call. When Mr. A dials the third party's telephonenumber in the same manner as in the case of an outgoing call from thehome area, the first class exchange receives the outgoing signal fromthe portable telephone set PID₁ via the key service unit SID₂ andconfirms, as a result of retrieving the subscriber information memory,that the current position of the portable telephone set PID₁ has beenregistered in the key service unit SID₂ in the first class roam area.Then the first class exchange instructs its charging section to chargethe telephone rate to the account of the portable telephone set PID₁ atthe point of commencement of the communication.

The first class exchange checks the telephone number of the called partyand sends a call signal to him via a predetermined route in the samemanner as in the case of an ordinary telephone.

An incoming signal to the portable telephone set PID₁ is alsotransmitted to the first class exchange as is the case with an incomingcall in the ordinary telephone. When the first class exchange recognizesthat the called party is the portable telephone set PID₁ (Thisrecognition is easy because the PID signal differs in structure from anordinary telephone number.), it retrieves its subscriber informationmemory to check whether the called portable telephone set is in the homearea or not. Having recognized that the portable telephone set PID₁ hasbeen registered in the key service unit SID₂, the first class exchangetransmits the incoming signal destined for the portable telephone setPID₂ to the key service unit SID₂. Upon receiving the signal, the keyservice unit SID₂ retrieves its PID signal memory to confirm that theportable telephone set SID₂ has been registered in its service area.Then the key service unit SID₂ sends out the PID₁ signal to the portabletelephone set PID₁, using the down control channel. The portabletelephone set PID₁ receives the signal and rings its bell, and uponhaving it off, Mr. A can communicate with the calling party. In thisinstance, the first class exchange sends out a ring-back tone to thecalling party in the same manner as in the case of an ordinarytelephone.

As described above, when the portable telephone set stays in thevicinity of its home area, its position is registered in the subscriberinformation memory of the first class exchange alone; namely, theregistration does not take place in the second class and higher classexchanges. The reason for this is that since Mr. A stays in the servicearea of the first class exchange, there is no need of intervention bythe higher class exchanges. In other words, an incoming call signal fromany telephone set throughout the country is transmitted to the portabletelephone set through the first class exchange, and accordingly it issufficient only to retrieve the subscriber information memory of thefirst class exchange (which administers the first class roam area).

While in the above Mr. A's portable telephone has been described to beheld in the ON state, it is considered that the portable telephone setis normally in the OFF state and turned ON only when Mr. A wants tooriginate an outgoing call. In this case, however, when an incoming calloccurs, the first class exchange calls the portable telephone set,regarding that it stays in its home area, because its current positionhas not been registered in the subscriber information (the positionregistration memory) of the first class exchange. Where a fixedtelephone set is provided in the home area in association with theportable telephone set, its bell is rung; if not, the first classexchange judges, after a certain elapsed time, that the called portabletelephone set is not in the home area, and automatically gives thecalling party an answer "The portable telephone set you are calling isnot in the home area." Therefore, a user who needs to call and to becalled with extraordinary frequency, such as a salesman or doctor willkeep his postable telephone set in the ON state.

Now, assume that Mr. A wants to originate an outgoing call after havingarrived at the park and that portable telephone key service units areinstalled on poles in some places in the park so that the portabletelephone set can communicate with any one of the key service unitsanywhere in the park. When Mr. A turns ON his portable telephone set,its radio section acquires the down control channel from the nearest keyservice unit SID₃. Then the portable telephone set stores an SID₃ signalof the key service unit SID₃ in its memory and transmits thereto thePID₁ signal through the up control channel. The key service unit SID₃stores the PID₁ information in its memory and, at the same time, sendsout a position registration request signal (PID₁ +SID₃) to the firstclass exchange. Then the first class exchange transfers the signal tothe position registration memory of its subscriber information memory,in which the position of the portable telephone set PID₁ registereduntil then is cancelled and instead its current position in the servicearea of the key service unit SID₃ is stored.

Thus the registration of the current position of the portable telephoneset PID₁ is completed. After this, outgoing and incoming calls can behandled in the same manner as in the case where the portable telephoneset PID₁ is always held in the ON state.

Now, consider that when Mr. A was going under the railroad tracks on hisway home, the portable telephone set held in the ON state rang. Sincethe timbre of this ringing was different from the timbre in the case ofan incoming call from the key service unit, Mr. A could easilyunderstood that the call was sent from a wide area portable telephoneset calling first class radio base station. Since a red lamp was lightedon the display of the portable telephone set, Mr. A did not press thecall button (which acts as an incoming call receiving button in thiscase). After he passed through the underpass, the blue lamp was lightedin place of the red lamp, so Mr. A pressed the call button and couldcommunicate with the calling party.

ii) Outgoing and incoming call in second class roam area

Next, let it be assumed that after having reached home Mr. A decided togo to his office in his own car. His office was situated in the samecity as his home (Hoya-shi, Tokyo, for example) but in a telephoneexchange service area (the second class roam area) different from thehome area of his portable telephone PID₁. Mr. A's car was equipped witha car telephone, he can freely contact anyone by phone. But when hehappens to have a ride in someone's car also provided with a cartelephone, he will scarcely use it because he does not feel like usingit without permission. In such a case, since the portable telephonesystem of the present invention can be superposed on the land mobileradio telephone system as described previously, Mr. A can use hisportable telephone in another person's car and the telephone rate ischarged to the account of his portable telephone set without beingmischarged to the account of the another person's car telephone.

Assume that Mr. A has arrived at his office without using the cartelephone on his way to the office.

Before entering the office he went to a nearly tailor's shop to buy abusiness suit and paid for the suit on credit, using his portabletelephone set PID₁. This can be done as described previously. On his wayto the office Mr. A turned ON the portable telephone set for an outgoingcall. In this instance, the portable telephone set PID₁ acquires thedown control channel of a portable telephone key service unit (SID₃)mounted on the nearest pole and transmits a current positionregistration request signal to the subscriber information memory (theposition registration memory) of a first class exchange KTC-I-2 whichadministers the key service unit SID₃, as described previously. Theexchange KTC-I-2 judges, from the transmitted PID₁ signal, that theportable telephone set PID₁ has its home area in another first classexchange (KTC-I-1). Then the exchange KTC-I-2 stores in its positionregistration memory the position registration (PID₁ +SID₃) of theportable telephone set PID₁ and sends a position registration signal toa second class exchange (KTC-II-1 ) which administers the key serviceunit SID₃ and the portable telephone set PID₁ (that is, administers thesecond class roam area; namely, the exchange KTC-I-2 notifies theexchange KTC-II-1 that the key service unit has been requested toregister the position of the portable telephone set PID₁ which issubordinate to the exchange KTC-I-1.

The second class exchange KTC-II-1 stores the transmitted information inthe position registration memory of its subscriber information memoryand transfers the position registration signal from the exchange KTC-I-2to a first class exchange (KTC-I-1) which is subordinate to the exchangeKTC-II-1 and administers the home area of the portable telephone setPID₁ ; namely, the exchange KTC-II-1 requests the exchange KTC-I-1 toregister (or rewrite) the position of the portable telephone set PID₁ inthe position registration memory of its subscriber information memory.Then the first class exchange KTC-I-1 rewrites the information in itssubscriber information memory accordingly.

After this, the portable telephone set PID₁ is able to originate anoutgoing call to any place in the country. The operation of the networkfor the outgoing call is exactly identical with the operation in thecase of the aforementioned outgoing call in the park; so no descriptionwill be repeated in this connection. The telephone fare is charged tothe account of the portable telephone set PID₁ in the charginginformation storage area of the subscriber information memory of thefirst class exchange and the charging information is regularlytransferred once a month to the charging information storage area of thefirst class exchange which administers the home area of the portabletelephone set PID₁ so that a whole month's bill of telephone charges issubmitted to Mr. A.

Next, a description will be given of an incoming call to Mr. A'sportable telephone set PID₁. After registration of its position theportable telephone set PID₁ is in the state in which it is capable ofreceiving an incoming call. Where the calling telephone set issubordinate to the first class exchange KTC-I-1 which administers thehome area of the portable telephone set PID₁, the current position ofthe called portable telephone set PID₁ is found in the level of theexchange KTC-I-1 and the incoming call signal is transferred via thesecond class exchange KTC-II-1 to the exchange KTC-I-2, performing theincoming call operation for the portable telephone set PID₁.

In the case of a call from a telephone set subordinate to the firstclass exchange KTC-I-2 which administers the key service unit SID₃ inthe first class roam area, the search for the current position of theportable telephone set PID₁ is accomplished by the exchange KTC-I-2alone.

Where a call comes from a higher class roam area, for example, thesecond class one, the call signal is provided to the second classexchange KTC-II-2. The exchange KTC-II-2 analyzes the call signal and,when finding that the call signal is destined for the portable telephoneset PID₁, it searches its subscriber information memory for the positionregistration of the called portable telephone set PID₁. As a result ofthis, the exchange KTC-II-2 confirms that the portable telephone setPID₁ is in the roam area of the first class exchange KTC-I-2 subordinateto the exchange KTC-II-1 and transfers the incoming call signal to theexchange KTC-I-2. The exchange KTC-I-2 searches its subscriberinformation memory for the registered current position of the portabletelephone set PID₁ and then sends out the incoming call signal via thekey service unit SID₃ to the portable telephone set PID₁, ringing itsbell. Upon hanging off his portable telephone set PID₁, Mr. A can startcommunication with the calling party.

The above has described the cases where the communication is concludedwithin the second class roam area. The following will describe how thesystem of the present invention operates in the case where the portabletelephone subscriber has moved from the first class roam area to thesecond class one, with the portable telephone set held in the ON state,in the stand-by state, or in the busy state.

Now, let it be assumed that Mr. A walks from his home (in Hoya-shi) tothe office, with the portable telephone set PID₁ held in the ON state.As described previously, when Mr. A leaves the home area of his house,the portable telephone set PID₁ receives the down control channel signalfrom a portable telephone key service unit installed in the nearestthird party's house or mounted on the nearest telephone or electriclight pole and the portable telephone set PID₁ responds to the downcontrol channel signal to send out the PID₁ signal through the upcontrol channel, registering its current position. When Mr. A has gotout of the service area of the first class exchange KTC-I-1, theportable telephone set PID₁ similarly sends out the PID₁ signal to a keyservice unit installed there (which key service unit is subordinate to afirst class exchange KTC-I-2 different from the above-mentioned). Thefirst class exchange KTC-I-2 (also installed in Hoya-shi), which hasreceived the PID₁ signal from the portable telephone set PID₁ via thekey service unit, checks the PID₁ signal and finds that the portabletelephone set PID₁ is subordinate to another first class exchangeKTC-I-1. Then the first class exchange KTC-I-2 sends the positionregistration signal (the PID₁ signal) of the portable telephone set PID₁to the second class exchange KTC-II-1 which administers the exchangeKTC-I-2. The second class exchange KTC-II-1 stores the PID₁ +SID_(n)signal in its subscriber information memory and instructs theregistration of the current position of the portable telephone set PID₁to the first class exchange KTC-I-1 which is subordinate to the secondclass exchange KTC-II-1 and administers the home area of the portabletelephone set PID₁.

Thus the position of the portable telephone set PID₁ in the second classroam area is registered, after which the portable telephone set PID₁ iscapable of performing the outgoing and incoming call operations.

In the above the changing of the roam area has been described to takeplace when the portable telephone set PID₁ remains in the stand-bystate; in this case, if the portable telephone set PID₁ is busy, thecommunication channel is changed corresponding to the change of the roamarea and the position of the portable telephone set PID₁ is registeredin a similar way.

iii) Incoming call in third roam area

Now, assume that Mr. A calls on his friend who live in Musashino-shi (athird roam area) and, on his way, he calls up his friend by the portabletelephone set PID₁ to ask the direction to the friend's home.

Upon turning ON the power source the portable telephone set PID₁ sendsthe position registration request signal to the subscriber informationmemory (the position registration area) the first class exchange(KTC-I-3) which administers the area concerned. The subscriberinformation memory of the first class exchange KTC-I-3 checks the PID₁signal of the portable telephone set PID₁ and finds that the portabletelephone set PID₁ has the home area in another city. The exchangeKTC-I-3 stores the PID₁ information in its subscriber information memoryand notified a second class exchange (KTC-II-2), which administers theexchange (KTC-I-3), that the portable telephone set PID₁ has requestedto register its position. The second class exchange KTC-II-2 stores thetransmitted signal in its subscriber information memory and checks thesignal. As a result of this, the exchange KTC-II-2 finds that theportable telephone set PID₁ has the home area in another city, andtransfers the signal to a third class exchange (KTC-III-1) whichadministers the exchange KTC-II-2.

The third class exchange KTC-III-1 stores the signal in its subscriberinformation memory and requests the second and first class exchanges,which administer the portable telephone set PID₁, to store the positionregistration of the portable telephone set PID₁.

It will be seen from the foregoing description that upon completion ofthe above-described operations Mr. A's portable telephone set PID₁ isable to communicate with any telephone set all over the country. Whilein the above Mr. A is described to ask the way to his friend's homethrough use of the portable telephone set, he need not always use thismethod but may also request the exchange KTC-I of the guide servicedescribed previously.

iv) Outgoing and incoming calls in fourth class roam area

Now, let be assumed that one day Mr. A made a business trip to Takasaki(fourth roam area) by train and held the portable telephone set in theON state on his way to Takasaki so as to receive an incoming call fromhis office and that the portable telephone set rang to indicate anincoming call about 15 minutes before arriving at Takasaki. Each coachof the train is equipped with a portable telephone key service unit andthe portable telephone set which has registered its position in the keyservice unit is superposed on the train radio telephone system. That is,when an incoming call to a passenger (Mr. A) of the train occurs, theincoming call signal is sent from a train radio base station to thetrain with Mr. A aboard, and a train radio controller confirms theposition registration of Mr. A's portable telephone set, decides the keyservice unit which calls the portable telephone set, and sends theincoming call signal to the key service unit. The subsequent operationsare the same as in the case of an incoming call to an ordinary telephoneset. There is a case where only one or two train public telephone setsare provided in one train. In this case, the incoming call signal istransmitted directly to the portable telephone set from a wide areaportable telephone set calling fourth class base station. The calledsubscriber connects the portable telephone set to a nearby train publictelephone set through a connection unit to receive the incoming call.

When Mr. A was walking down the street a while after he had got off thetrain at Takasaki station he turned ON the power source of the portabletelephone so as to call his office in Musashino-shi. Then the positionof the portable telephone set was registered in the subscriberinformation memories of the following exchanges through the sameprocesses as described previously.

(a) First to third class exchanges which administer the roam area wherethe portable telephone set stays

(b) First to fourth class exchange which administer the home area of theportable telephone set

After this the portable telephone set is capable of performing theoutgoing and incoming call operations.

Mr. A finished his business at Takasaki and decided to enjoy golfing ata golf club in this district on the weekend. Mr. A was a member of thegolf club and presented the portable telephone set to a receptionist ofthe golf club in answer to a request to show his membership card ortelephone set. By calling the receptionist's key service unit from Mr.A's portable telephone set, the receptionist could check ID (GPID)information of the golf club and could immediately confirm that Mr. Awas a member of the club.

Mr. A enjoyed golfing on the weekend and then went home.

One day Mr. and Mrs. A went to a spa in Minami-Kishu for a week. Theycarried portable telephone sets with them separately and made full useof them while they went sight-seeing. The sunday of the week fell on avoting day of the general election. Conventionally, absentee voting hadinvolved troublesome procedures. In 2000's, however, the electorate willbe able to vote at any polling station all over the country, without thenecessity of taking such troublesome procedures. The portable telephoneset of the present invention which is capable of performing the outgoingand incoming call operation throughout the country will greatlycontribute to the above absentee voting. The reason for this is that theportable telephone set possesses the function of identifying its ownerand the function of a ballot, as described previously. Each voterregisters, before the voting day, the voting station, the time ofvoting, the PID information of the portable telephone set to be used forvoting, ID (election ID) information, his voiceprint, and informationabout the voter (his birthplace, birthday, permanent address, family,etc.). On the voting day the voter originate an outgoing call from hisportable telephone set at the registered voting station (anadministration center) at the registered time. The administration centerconfirms the PID and election ID information of the voter, checks hisvoiceprint, and makes inquiries about his birthplace and birthday, etc.(by automatic questioning and checking of replies by voice). After thechecking the voter is allowed to proceed to the voting operation. Mr.and Mrs. A effected the absentee voting in this way. Incidentally, uponcompletion of voting the election ID information used by Mr. and Mrs. Ais automatically erased, preventing that a third party votes using theportable telephone sets.

v) Outgoing and incoming call in fifth roam area

Now, assume that Mr. A went to Hokkaido carrying the portable telephoneset a little after the sight-seeing tour to Minami-Kishu. Upon turningON the power source of the portable telephone set, its position wasregistered in the subscriber information memories of the followingexchanges, enabling the portable telephone set to perform the outgoingand incoming call operations.

(1) First to fourth class exchanges which administer the roam area ofthe portable telephone set.

(2) First to fifth class exchanges which administer the home area of theportable telephone set

vi) Use of the portable telephone set in the wide area calling mode andutilization of the position sensing function

Mr. A's son, B who was a university student, planned to climb the JapanAlps in the summer vacation, and decided to take his portable telephoneset at the advice of his father, and he had requested, in advance, anexchange KTC-V to call him by a satellite. When he was traversing theridge of the Japan Alps, his portable telephone set held in the stand-bystate rang. Since the timbre of this ringing was different from thetimbre of calling from the portable telephone key service unit or thewide area portable telephone calling first, second, third or fourthclass base station, Mr. B could easily understand that the call was madefrom the wide area portable telephone set calling fifth class basestation. He found a message "Good luck. Ichiro Ando" displayed on thedisplay of the portable telephone set, and from which he learned that itwas an encouraging telegram from his friend.

One day Mr. and Mrs. A went to an amusement park together with theirson, his wife and grandchildren. Since it was considered that it wouldbe difficult for them to get contact with one another if they shouldstrayed from one another, they each carried a portable telephone set.Further, Mr. A let his grandchildren have portable telephone sets (heldin the ON state) as substitutes for their identification tags. Mr. andMrs. A, their son and his wife, and their grandchildren scattered overthe amusement part, but when one of the grandchildren got lost, theycould immediately found the lost grandchild. Moreover, they could easilyget contact with one another to determine the meeting time and place,etc.

vii) Omission of the position registration of the portable telephone setin the exchange which administers the roam area

With a view to technically clarifying that the portable telephone set ofthe present invention can be used in a roam area, the present inventionhas been described on the precondition that the position of the portabletelephone set is registered not only in the exchange which administersits home area but also in the exchange which administers its roam area.However, the registration in the latter exchange need not always beeffected; but in this case, there would be the following defects:

(1) Upon each occurrence of the outgoing call from the portabletelephone set, outgoing call information (the charging information) mustbe provided to an exchange (any one of first to fifth class exchanges)which administers the home area of the portable telephone.

(2) Even if an incoming call to the portable telephone set is anincoming call from an area near the roam area of the portable telephoneset, it is necessary, for inquiring about the current position of theportable telephone set, to transmit the incoming call signal to thefifth to first class exchanges which administer the home area of theportable telephone. (see FIGS. 11A to 11G)

As is the case with the above, in the case where the memory of theexchange which administers the home area of the portable telephone sethas stored the positional information of the portable telephone set inthe roam area administered by a plurality of exchanges, theabove-mentioned omission of the position registration will not cause thesystem to be inoperable, but the above-said operations (1) and (2) willbe needed.

viii) Function of the fixed telephone set provided in the home area ofthe portable telephone set in association therewith

Where the fixed telephone set is provided in association with theportable telephone set, it is possible to obtain the following functionsby deriving the current positional information of the portable telephoneset from the positional information memory of the first class exchange.

(1) Where an incoming call occurs to the portable telephone set whichhas registered its position in the roam area, if the portable telephonedoes not answer for a predetermined period of time by some cause, theincoming call is transferred to the fixed telephone set in the home areaof the portable telephone set. It is possible, in this case, to displayon the fixed telephone set the telephone number of the calling party andthe registered current position of the portable telephone set.

(2) When the portable telephone subscriber returns to his desk, it ispossible to read out outgoing and incoming calls produced or messagesrecorded in his absence.

(11) Effect of the Invention

The portable telephone system of the present invention permits efficientestablishment of a communication channel at any time and at any place,whether indoors or outdoors; this has been considered impossible fromthe technical and economical points of view. Accordingly, the presentinvention is of great utility in offering convenience in various phasesof social life. Furthermore, the portable telephone set of the presentinvention provide great advantage in social life by using its functionsother than the comminication one, in particular, by utilizing theportable telephone set for identifying its owner as the credit functionand as enhanced functions of IC or similar cards.

What I claim is:
 1. A portable telephone system in which a plurality ofi-th class exchanges, which accommodate directly or through at least one(i-1)th class exchange, at least one key service unit of a plurality ofportable telephone sets present in each service area, and at least one(i+1)th class exchange, which accommodates the plurality of i-th classexchanges through junction lines, are stratified to form an exchangesystem so that i=2, 3, 4, 5 and so that the (i+1)th class exchangecovers all of the service areas through the i-th class exchange, saidnumber i being equal to a number of stratified steps minus one, saidexchange system having a function whereby information which specifies ahome area predetermined from the service areas for each of the portabletelephone sets and the portable telephone sets in distinction from eachother is registered in a memory in each of the (i-1)th class and i-thclass exchanges and in a memory in the (i+1)th class exchange whichadminister the home area.
 2. A channel setting system in a portabletelephone system, in which a plurality of i-th class exchanges, whichaccommodate directly or through at least one (i-1)th class exchange, atleast one key service unit of a plurality of portable telephone setspresent in each service area, and at least one (i+1)th class exchange,which accommodates the plurality of i-th class exchanges throughjunction lines, are stratified to form an exchange so that i=2, 3, 4, 5and so that the (i+1)th class exchange covers all of the service areasthrough the i-th class exchanges, said number i being equal to a numberof stratified steps minus one, said exchange system having a functionwhereby information which specifies a home area predetermined from theservice areas for each of the portable telephone sets and the portabletelephone sets in distinction from each other is registered in a memoryin each of the (i-1)th class and i-th class exchanges and in a memory inthe (i+1)th class exchange which administer the home area and the(i+1)th class exchange; and in whicha wide area communication i-th radiobase station is provided for a plurality of portable telephone setswhich are connected to one of the i-th class exchanges and are capableof being called and transmitting a communication signal in the same areaas the service area of said one of the i-th class exchanges;self-identification information of each of the plurality of portabletelephone sets contains self-identification information corresponding tothe i-th and (i+1)th class exchanges; in a case where any one of theportable telephone sets is called from a calling party of an incomingcall in the service area of said one of the (i-1)th class or i-th classexchanges and does not answer to an incoming call signal from the keyservice unit in which a staying location of the called one of theportable telephone sets has been registered, the i-th radio base stationperforms wide area calling; and when the called one of the portabletelephone sets has sent back an answer signal to said one of the i-thclass exchanges through the key service unit in the service area orthrough some other transmitting means during a fixed period of time,communication channels are set up between said one of the i-th classexchanges or any one of the (i-1), (i-2), . . . exchanges and firstclass radio base stations and the called one of the portable telephonesets and between the key service unit and the called one of the portabletelephone sets.
 3. A channel setting system in a portable telephonesystem, in which a plurality of i-th class exchanges, which accommodatedirectly or through at least one (i-1)th class exchange, at least onekey service unit of a plurality of portable telephone sets present ineach service area, and at least one (i+1)th class exchange, whichaccommodates the plurality of i-th class exchanges through junctionlines, are stratified to form an exchange system so that i=2, 3, 4, 5and so that the (i+1)th class exchange covers all of the service areasthrough the i-th class exchanges, said number i being equal to thenumber of stratified steps minus one, said exchange system having afunction whereby information which specifies a home area predeterminedas a usual staying service area for each of the portable telephone setsand the portable telephone sets in distinction from each other isregistered in a memory in each of the (i-1)th class and i-th classexchanges and in a memory in the (i+1)th class exchanges whichadminister the home area and in a memory in each of the (i-1)th classand i-th class exchanges which administer the service area where any oneof the portable telephone sets is present;and in which a wide areacommunication i-th radio base station is provided for a plurality ofportable telephone sets which are connected to one of the i-th classexchanges and are capable of being called and transmitting acommunication signal in the same area as the service area of said one ofthe (i-1)th class or i-th class exchanges; self-identificationinformation of each of the plurality of portable telephone sets containsself-identification information corresponding to the i-th and (i+1)thclass exchanges; in a case where any one of the portable telephone setsis called from a calling party of an incoming call in the service areaof said one of the i-th class exchanges and does not answer to anincoming call signal from the key service unit in which a stayinglocation of the called one of the portable telephone sets has beenregistered, the (i-1)th class or i-th radio base station performs widearea calling; and when the called one of the portable telephone sets hassent back an answer signal to said one of the i-th class exchangesthrough the key service unit in the service area or through some othertransmitting means during a fixed period of time, communication channelsare set up between said one of the i-th class exchanges or any one ofthe (i-1), (i-2), . . . exchanges and first class radio base stationsand the called one of the portable telephone sets and between the keyservice unit and the called one of the portable telephone sets.
 4. Achannel setting system in a portable telephone system, in which aplurality of i-th class exchanges, which accommodate directly or throughat least one (i-1) class exchange, at least one key service unit of aplurality of portable telephone sets present in each service area, andat least one (i+1)th class exchange, which accommodates the plurality ofi-th class exchanges through junction lines, are stratified to form anexchange system so that i=2, 3, 4, 5 and so that the (i+1)th classexchange covers all of the service areas through the i-th classexchanges, said number i being equal to the number of stratified stepsminus one, said exchange system having a function whereby informationwhich specifies a home area predetermined as a usual staying servicearea for each of the portable telephone sets and the portable telephonesets in distinction from each other is registered in a memory in each ofthe (i-1)th class and i-th class exchanges and in a memory in the(i+1)th class exchanges which administer the home area and in a memoryin each of the (i-1)th class and i-th class exchanges which administersthe service area where any one of the portable telephone sets ispresent;and in which a wide area communication i-th radio base stationis provided for a plurality of portable telephone sets which areconnected to one of the i-th class exchanges and are capable of beingcalled and transmitting a communication signal in the same area as theservice area of said one of the i-th class or i-th class exchanges;self-identification information of each of the plurality of portabletelephone sets contains self-identification information corresponding tothe i-th and (i+1)th class exchanges; in a case where any one of theportable telephone sets is called from a calling party of an incomingcall in the service area of said one of the i-th class exchanges anddoes not answer to an incoming call signal from the key service unit inwhich a staying location of the called one of the portable telephonesets has been registered, the (i-1)th class or i-th radio base stationperforms wide area calling; and when the called one of the portabletelephone sets has sent back an answer signal to said one of the i-thclass exchanges through the key service unit in the service area orthrough some other transmitting means during a fixed period of time,communication channels are set up between said one of the i-th classexchanges or any one of the (i-1), (i-2), . . . exchanges and firstclass radio base stations and the called one of the portable telephonesets and between the key service unit and the called one of the portabletelephone sets, and said self-identification information includessufficient data correlating the self-identification number to specificindividual subscribers so that the self-identification is usable in anidentification mode of the individual portable telephone sets and thesubscribers so that the information is usable as credit cardinformation, ID card information and cash card information.
 5. A channelsetting system in a portable telephone system according to claim 4,including means for indicating via a portable telephone headset as thephysical location of another portable telephone head set is located as afunction of the self-identification information of said another portabletelephone headset.
 6. A channel setting system in a portable telephonesystem according to claim 4, in which said self-identificationinformation comprises means including a digit code of thirteen digitsfor identification of an individual phone subscriber.